Science 4

A moving loop cuts through a magnetic field, which generates current in the wire.Types of Generators• An a.c. generator is a rotating loop in a magnetic field which generates current that fluctuates in value and changes direction every half-rotation of the loop. The current produced is called alternating current (a.c.).• A simple d.c. generator is a rotating loop in a magnetic field which generates current that fluctuates in value but does not change direction.• The only difference between the simple a.c. and simple d.c. generator is the commutator used. An a.c. generator makes use of two slip rings while a d.c. generator makes use of a split ring commutator.2. What is a motor? One of the most important uses of electromagnetism is in the electric motor. Anelectric motor is a device that converts electrical energy to mechanical energy. Amotor contains a movable electromagnet. If an alternating current is supplied to theelectromagnet, its poles are reversed. Where it was once attracted by the opposite pole offixed magnet, it will next be repelled. This process is repeated many times each second.There are manytypes of electricmotors. Each isdesigned for aparticular purposeor use. They alloperate on theprinciple ofelectromagnetism. 19

3. What is a transformer? The alternating current through power lines is at an extremely high voltage. Beforealternating current from the power plant can enter your home, its voltage must bedecreased. The current must flow through a device called a transformer to decrease thevoltage. The transformer regulates the voltage that enters the system. The operation of atransformer operates on the principle of both electromagnetism and electromagneticinduction. A simple transformer is made of two coils of wire called the primary and thesecondary coils. These coils are wrapped around an iron core. As an alternating currentpasses through the primary coil, the iron core becomes an electromagnet. Because thecurrent changes direction many times each second, the magnetic field also changes itsdirection and induces an alternating current in the secondary coil.Schematic Diagram of the Parts of a Transformer What you will do Activity 3.3 Diagram AnalysisExamine the pictures of the two types of transformers, the step up and the step downtransformers. Differentiate a step-up transformer and the step-down transformer in terms ofthe number of turns in the coil. 20

Step-up Transformer Step-down Transformer_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________You’re right! The number of turns in the iron core determines the type of transformer. In astep-up transformer, the number of turns in the primary core is less than in the secondarycoil, while in the step-down transformer, the number of turns in the primary core is greaterthan in the secondary coil. A step-up transformer increases the voltage while a step-downtransformer decreases the voltage.What will you do? You want to use the appliance that was given to you by your Japanese friend. It issaid that its voltage is 100 volts. What will you do? Why?____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Key to answers on page 33What you will do Self-Test 3.1Match the phrase in COLUMN A with the term being described in COLUMN BCOLUMN A COLUMN B1. a small region in a piece of iron where a. electromagnetism atomic magnetic line up in the same direction b. armature c. circuit breaker2. ends of bar magnet d. commutator3. rotating coil in an electric motor e. electromagnet4. a device that converts mechanical energy f. electromagnetic into electric energy induction5. a device that converts electrical energy into g. generator h. magnetic domain mechanical energy6. the production of current in a wire that 21

is moving across a magnetic field i. magnetic field7. a device that regulates or controls the flow of j. rectifier k. transformer current l. magnetic8. current that reverses the direction of flow m. transistor9. increase the voltage supply n. temporary magnetism10. measures small amounts of electric current o. motor11. a property of some materials in which there p. magnetic poles q. generator is a force of repulsion or attraction between r. galvanometer like or unlike poles s. alternating current12. a temporary magnet made of a wire coil t. direct current through which an electric current passes u. step down transformer13. current that flows in only one direction v. step-up transformer14. the branch of physical science that involves the combined effects of electricity and magnetism15. induced magnetism Key to answers on page 33Lesson 4 Electricity at Home Human lifestyles have changed. Years ago, most people thought of electricity as littlemore than a curiosity for amusing people. To many scientists, however, it was aphenomenon to be studied in the laboratory. Today giant towers across the country carryelectricity to every corner of the land. Electricity has become indispensable to our way of life. Look around your home. You will find electric outlets in nearly every wall. This iswhere electrical appliances are plugged in order to function. You use electricity in manyways. Read this lesson and see how important electricity is in our daily life. A. Household Circuits When a house is built, an electrician must install electric outlets, wall switches, fuses, and circuit breakers. All of these devices must be connected by wires inside the walls. In one kind of installation, the wirings in the walls consist of plastic- insulated cable. This type of cable is a group of three wires enclosed in a plastic casing. One wire, insulated with its own black cover, is the “hot” wire. This carries the alternating current to the outlet of 220 volts. Caution: DON’T TOUCH THIS WIRE! When touched, it would produce a potential difference of 220 volts that would be 22

very dangerous. This could send enough current through your body to stop yourheart from beating. The white insulated wire has no potential but it carries the AC(alternating current) back out of the appliances and it might be dangerous to touch.The third wire has no insulation. This wire is connected directly to the ground and itcarries no current. This wire is a safety feature. BLACK “HOT”WIRE THIRD WIRE WHITE WIRE – (grounding)Electric CableElectric Outlet The electric cable is used to carry electric current to homes and other buildings. The electric outlet, the figure at the left side, is where you insert a plug. The flat prongs are connected to the black and white wires of the cable inside the wall. Current flows in one prong, through the appliance, and back into the wall through the other prong. The potential difference between the prongs causes current to flow, delivering energy to the appliance. The round outlet is a provision for the round prong that serves as the ground wire. If you live in an older type of house, the outlets may not have the grounding terminals.B. Short Circuits The 220-volt “hot” wire is very dangerous. Worn insulation or a poor connection can create a short circuit. A short circuit is any accidental connection that allows the current to go directly to the ground instead of passing through an appliance. A 220-volt potential difference can provide any enormous current if there is no appliance in the circuit to provide resistance. A short circuit can cause wires to carry more current than they were designed to carry. The wires can overheat and cause fires. In modern homes, the ground wire in the cable protects people against short circuits. The metal shell of an appliance is connected to the ground wire through the round, third terminal of the plug. If the “hot” wire touches the shell, the current goes directly to the ground through this lowest –resistance path. If you touch the shell of the grounded appliance, very little of the current will go through your body. Appliances that have plastic shell insulate the user from the current. Such appliances do not need to be connected to the ground. 23

C. Overloads Have you ever plugged several appliances into the same outlet? If you have, you may have overloaded the circuit. Wires may contain too much current when they are overloaded. An overload may cause the circuit to heat up and melt the wires, much as a short circuit would. Often, this kind of overload occurs in the kitchen. For this reason, kitchens are usually wired with thicker wires that carry more current without over heating. Why are kitchens likely places for circuit overload? D. Protecting the Circuits What you will do Activity 4.1 Locating and Examining a Fuse Box Have a parent or an adult help you locate and examine the fuse box or circuit breakerin your home. Answer the following questions: 1. Describe the appearance of the fuse. 2. How are these fuses rated? 3. How many are rated 15 Ampere, 30 Ampere and 60 Ampere? 4. If you have a circuit breaker at home, describe the set-up. Key to answers on page 34Read this! To prevent wire from overheating, circuits are protected against overloads and shortcircuits. This protection is often provided by a fuse. A fuse is a device containing a shortstrip of metal with a low melting point. If too much current passes through the metal, it melts,or “blows”, and breaks the circuit. This is your signal to find and correct the overload and toreplace the fuse. FUSE BOX Another device that protects circuit from overloads is a circuit breaker. One type of circuit breaker is a switch attached to a bimetallic strip of metal. When the metal gets hot, it bends, which opens, or “trips”, the circuit. This action does not harm the circuit breaker. After the problem has been corrected, the circuit breaker can be reset.Circuit Breaker 24

E. Power Transmission Thousands of powerful generators across the country produce electricity for use in houses and businesses. This energy is fed through a network of transmission lines called power grid. All these generators supplying you with electricity work on the basis of Faraday’s law of induction. Let’s recall: Faraday’s law of electromagnetic induction states that current can be induced in a loop by changing magnetic field that is passing through the loop. A power plant like an electric lamp works in the principle of electromagnetic induction. When a loop of wire spin within a magnetic field, current is induced in the wire. What you will do Activity 4.2Read the comic strips below. Answer the following questions: 1. How is power distributed from the power plant to the consumer? 2. Why is power transmitted at high voltage and low current through long distance? 3. To decrease power loss, transmission lines must have low resistance. What materials are used as transmission lines? 4. Transmission lines are large diameter wires made of several stranded thinner wires. Why are they made this way? 25

Source: Conceptual Physics by Paul Hewitt Key to answers on page 34This common sight is a transformer. This transformerlowers the voltage of electric current from power plantsof about 30,0000 volts to 220 volts that are received inyour houses.Large white ceramic insulators prevent highvoltage from arching to the ground. 26

What you will do Self-Test 4.1Match the function in COLUMN A with the parts in COLUMN BCOLUMN A COLUMN B1. part of a transformer A. electromagnet2. prevents short circuiting B. primary coil3. voltage transmitted to houses C. magnetic fields4. used as ground wire D. black wire5. Increases voltage E. magnetic north6. decreases voltage F. step-up transformer7. wire that supplies the voltage G. 220 volts8. network of transmission lines H. step-down transformer9. assembly of fuse in a fuse box I. white wire J. magnetic poles that help avoid overloading K. circuit breaker10.ends of a bar magnet L. fuse M. power grid Key to answers on page 34 Let’s summarize1. Magnets are objects that attract materials containing iron and that always face the same direction when moving freely2. Natural magnets are made of an iron ore called magnetite, or lodestone. They are permanent magnets. Artificial magnets, which are made by induced magnetism, are either permanent or temporary, depending upon the material they are made of. Materials such as iron that are strongly attracted by magnets are called ferromagnetic substances. Paramagnetic substances are only slightly attracted by magnets. Diamagnetic substances are slightly repelled by magnets.3. Magnetic lines of force indicate the presence and strength of magnetic force field. They extend from the magnetic north pole to the magnetic South Pole. Like poles of 27

magnet repel, unlike poles attract. The cause of magnetism is explained by the idea of magnetic domains.4. Magnetic and electric fields may induce one another. Coiling a conductor around an iron core makes electromagnets.5. Motors used electromagnetism to convert electrical energy to mechanical energy.6. Transformers and generators are based on electromagnetic induction. A conductor cutting magnetic lines of force induces a current. A step-up transformer increases the voltage. A step-down transformer decreases the voltage.7. Generators used electromagnetism to convert mechanical energy into electrical energy.8. A coil of wire with a current through it is an electromagnet that reverses when the current reverses direction. Alternating current and direct current are two types of current.9. A fuse and a circuit breaker are two devices that protect household circuits.10. Most electronic devices run on direct current. Rectifiers change alternating current into direct current.11. In all power plants, a large generator is connected to a turbine through a drive shaft. As the turbine rotates, it brings the generator with it, which generates electrical energy. Electrical energy from the power plant is transmitted at high voltage and low current to minimize power losses. Step-up transformers raise output voltage from generators before transmission.12. Electrical energy distribution begins at the first substation where the transmission voltage is initially reduced. At subsequent substations, voltage is further cut down. The final reduction of the voltage to 220 volts occurs at distribution transformers found on electric poles. From there, power is brought to houses through service wires. 28

PosttestI. Encircle the letter of the BEST ANSWER. 1. Materials that are strongly attracted to magnets are a. diamagnetic b. ferromagnetic c. paramagnetic d. All of the above 2. According to Michael Faraday, a. magnetic field produces current b. current produces magnetic field c. current is always present in a magnetic field d. wire carrying current produces magnetic field 3. How do you weaken a magnet? a. By heating it b. By banging it on a table c. By soaking it on a mercury d. By placing it near a compass 4. A piece of copper cannot be made into a magnet because a. copper cannot be charged. b. copper atoms have no charge. c. the domains are already aligned. d. electrons spinning in opposite direction in copper cancel each other. 5. To decrease the strength of an electromagnet a. add iron center to the coil. b. decrease the number of loops of wire in the coil. c. increase the number of loops of wire in the coil. d. All of the above 6. If the N pole of a magnet is brought near a magnet suspended on a string, the a. N poles attract each other b. N poles attract the S poles c. S poles attract each other d. N poles repel the S poles 29

7. In sending electric energy over long distance, the main cause of energy loss is a. the use of transformer. b. the size of the wires. c. the high current. d. the use of direct current.8. A material that allows the electromagnet in a motor to move is thea. amplifier. c. commutator.b. armature. d. semiconductor.9. A device that turns electric energy into a sound energy isa. a speaker. c. a CRT.b. a transformer. d. generator.10. A material that is slightly repelled by a magnet is calleda. diamagnetic. b. ferromagnetic.c. paramagnetic. d. all of these11. In a magnet the regions of greatest magnetic force are thea. magnetic domains. b. magnetic poles.c. lodestones . d. magnetic field.12. A compass needle points to the ________ pole.a. magnetic b. geographic c. closer d. at any point13. Clusters of many atoms that can be thought of as tiny magnets area. insulators. c. magnetic poles.b. magnetic domains. d. geographic poles.14. In a household electric circuit, a short circuit occurs when a. two hot wires touch. b. a hot wire is grounded. c. a fuse blows or a circuit breaker trips the circuit. d. a ground wire touches the metal shell of an appliance.15. High potentials are used in long-distance transmission of electricity because a. they are safer to use. b. there is no other way to make current flow. c. there is less loss of power when currents are small. d. generators produce high potentials with greater efficiency. 30

II. Match column A with column BCOLUMN A COLUMN B1. the combined effects of electricity and a. electromagnetic induction magnetism b. magnetic poles c. battery2. A magnet in which magnetism is produced by an electric current d. electromagnetism3. The creation of a current by a changing e. electric motor magnetic field f. electromagnet g. electric generator4. A machine that changes kinetic energy into h. voltage electric energy i. Transformer j. magnetism5. A machine that changes electric energy k magnequench into kinetic energy l. magnetic field m. temporary magnetism6. A device that increases or decreases voltage n. magnetic lines of force7. Tiny permanent magnets o. magnetites8. Magnets made from alloys of aluminum, p .permanent magnets q. alnico magnet cobalt and nickel9. Region in the space around a magnet in which a magnetic force acts on other magnet brought into the region10. magnet made mostly of iron, with little neodynmium and boron Key to answers on page 21 31

Key to AnswersPre-Test 6. d 11. bI. 1. d 7. b 12. a 8. d 13. c 2. a, b, d 9. d 14. b 3. c 10. d 15. b 4. b 5. bII. 1. South 6. domains 2. permanent 7. electromagnetism 3. south-seeking pole 8. repel 4. poles 9. ferromagnetic 5. magnetic field 10. lodestoneLesson 1Self-Test 1.1 1. lodestone 2. magnetic 3. Magnes 4. magnet 5. ThalesLesson 2Possible answers to:Activity 2.1a:3. The paper clips were attracted to the screw driverActivity 2.2 1. The S pole of the suspended magnet is attracted to the N pole of the other magnet 2. The N pole of the suspended magnet repelled the N pole of the magnet 3. The N pole of the suspended magnet was attracted to the S pole of the other magnet 4. The S pole of the other magnet repelled the S pole of the suspended magnet. 32

Self-Test 2.1: 1. ALNICO 2. DOMAINS 3. MAGNETIC FIELD 4. MAGNETIC LINES OF FORCE 5. FERROMAGNETIC 6. DIAMAGNETIC 7. PARAMGANETIC 8. MAGNET 9. MAGNETIZATION 10. POLESLesson 3Possible answers to Activity 3.1 1. The iron nails, paper clips and pins were attracted to the iron coil when the circuit is connected to the dry cell. 2. The iron nails, paper clips and pins dropped when the circuit is disconnected to the dry cell.Possible answers to Activity 3.2In diagram A, the pointer of the galvanometer deflected to the rightIn diagram B, the pointer of the galvanometer deflected to the leftThere is current when the magnet in placed in between the poles of the magnet.What you will do? Use a step-up transformer. Because the output here in the Philippines is 220 volts.So, to make the voltage 220, a step-up transformer is needed.Self-Test 3.1 6. f 11. l1. h 7. k 12. e2. p 8. s 13. t3. b 9. u 14. a4. q 10. r 15. n5. o 33

Lesson 4The answers to ACTIVITY 4.1 are in the discussion.Possible answers to Activity 4.21. Electric power is transmitted and distributed at high voltage and low current from the power plant to the consumer through transmission lines.2. Output voltage from generators is first increased through step up transformer at the power plant before the electric power is transmitted. The voltage of the electric power is reduced to a value suited to the consumer’s needs. Transformers are used to step up and step down the voltage in substation.)3. Electric power is transmitted at high voltage and low current to minimize power loses. Copper wires are used as transmission lines.4. The transmission lines need to be big diameter wires because they carry large current. But big solid wires are difficult to handle. Hence, thinner wires are stranded to have flexible strong diameter wires.)Self-Test 4.11. B 5. F 9. K2. L 6. H 10. J3. G 7. D4. I 8. MPosttestI. Multiple Choice 11. b 1. b 6. b 12. b 2. d 7. b 13. b 3. c 8. c 14. a 4. d 9. a 15. c 5. b 10. aII. Matching Type: 1. d 2. f 3. a 4. g 5. e 6. i 7. o 8. q 9. b 10. k 34

-End of Module-ReferencesMurphy & Smooth, (1998). Physics principles and problems, Toronto, Canada: Charles E. Merill Publishing Co.Eby & Horton, (1986). Physical science, New York: Macmillan Publishing CompanyJones & Childers, (1992). Contemporary college physics, 2nd Ed, California: Addison-Wesley Publishing CompanyPaul Hewitt, (1998). Conceptual physics, CA: Saunders Publishing 35

Module 9 Going Places What this module is about Loops and roller coasters are very interesting rides. Have you ever tried one? Did you experience the sudden jerks and lurks? And what about the sudden turn around the loops? Aren’t they amazing? We never fall off our seats! That’s Physics. Physics is a very interesting course. It is usually described as the study of matter and energy, which includes several branches such as mechanics, thermodynamics, electricity and magnetism, waves and optics, and relativity and atomic physics. Mechanics includes the concepts about motion and its causes. Kinematics is said to be the quantitative description of the motion of the objects. Dynamics, on the other hand, includes concepts about the causes of motion. Mechanics provides explanations of many phenomena such as the motion ofskydivers, the parachutes, and why we jerk when the vehicle suddenly stops. In this module you will learn many things about Physics particularly about motion.This module includes four (4) lessons such as:  Lesson 1 - Describing Motion  Lesson 2 - Linear Motion  Lesson 3 - Curvilinear Motion  Lesson 4 - Physics and Transportation Read, enjoy, and discover the secrets of Physics! What you are expected to learn After going through the module, you are expected to: 1. define the fundamental principles of mechanics, specifically motion; 2. apply the concepts and principles in mechanics to practical situations and problems; 1

3. trace the development in transportation facilities from the animal-driven to engine- powered vehicles. 4. solve problems in a logical and organized manner; and, 5. develop appreciation of physics. How to learn from this module Here’s a simple guide for you in going about the module. 1. Read and follow the instructions very carefully. 2. Take the pretest. It is a simple multiple-choice test provided at the start to determine how much you know about the content of this module. 3. Check your answers against the correct answers provided at the last page of the module. 4. Be very honest in taking the test so you know how much knowledge you already have about the topic. 5. Read the different lessons about the earth, sun and moon. 6. Perform all the activities, as these will help you have a better understanding of the topic. 7. Take the self-tests at the end of each lesson to determine how much you remember about the lesson. 8. Finally, take the posttest at the end of this module. Good Luck and have fun! What to do before (Pretest)Direction: Choose the letter of the best answer. Write your answer on a separatesheet of paper. 1. When you look at the speedometer in a moving car, you can see the car’s ________. a. average speed b. average acceleration c. instantaneous speed d. instantaneous acceleration 2. Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 km/h. Which of the following is NOT true? a. Your speed is constant b. Your velocity is constant c. You and the car are accelerating. 2

3. A ball is thrown straight up. At the top of its path its acceleration is ______________. a. 0 m/s2 b. about 5 m/s2 c. about 10 m/s2 d. about 20 m/s24. If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first? a. The coin b. The feather c. Neither – they will both reach the bottom at the same time.5. At what part of a path does a projectile have minimum speed? a. when it is thrown b. half-way to the top c. at the top of its path d. when it returns to the ground6. A ball is thrown straight up. What is its acceleration before it strikes the ground? a. 0 m/s2 b. about 5 m/s2 c. about 10 m/s2 d. about 20 m/s27. A ball is thrown straight up. After 2 seconds what is the acceleration of the ball? a. 0 m/s2 b. about 5 m/s2 c. about 10 m/s2 d. about 20 m/s28. In the absence of air friction, the vertical component of a projectile’s velocity doesn’tchange as the projectile moves. a. always true b. always false c. sometimes true9. If a freely falling object were somehow equipped with an speedometer, by how muchwould its speed reading would increase each second? a. about 5 m/s b. about 10 m/s c. about 15 m/s d. A variable amount10. A ball is thrown vertically upward. What is its velocity at the top of its path? a. 0 b. 5 m/s 3

c. 10 m/s d. 10 m/s2 11. A ball is thrown vertically upward. What is its acceleration at its maximum height? a. 0 b. 5 m/s c. 10 m/s d. 10 m/s2 12. A ball is thrown vertically upward. What is its acceleration after about 1 second? a. 0 b. 5 m/s c. 10 m/s d. 10 m/s2 13. A ball is thrown vertically upward, with an initial velocity of 50 m/s and caught back at the same level as when it was thrown. What is the velocity of the ball at that point? a. 50 m/s b. 50 m/s, downward c. 9.8 m/s d. 9.8 m/s2 14. What force is exerted on the ball at the top of its path? a. 9.8 N b. 9.8 N c. Gravitational force d. Force exerted by the hand that threw the ball 15. What do you call the motion of an object with a constant acceleration? a. Motion b. Uniform Motion c. Constant Motion d. Uniformly Accelerated Motion 16. A ball is thrown vertically upward. What is its instantaneous speed at its maximum height? a. 0 b. 5 m/s c. 9.8 m/s d. 9.8 m/s217. If you whirl a tin can on the end of a string and the string suddenly breaks, the tin can will a. fly directly toward you. b. fly directly away from you. c. spiral away from your hand. d. fly off tangent to its circular path. 4

18. Which of the following would not be considered as projectile? a. A cannonball rolling down a slope. b. A cannonball thrown through the air. c. A cannonball rolling off the edge of a table. d. All of the above.19. A ladybug rests at the bottom of a tin can that is being whirled horizontally on the end of a string. Since like the tin the ladybug can moves in a circle, there must be a force on it. What exerts this force? A. gravity B. your hand C. the tin can D. the string 20. Acceleration is defined as the CHANGE in ______________. a. distance divided by the time interval b. velocity divided by the time interval c. time it takes to move from one speed to another d. time it takes to move from one place to another Key to answers on page 32Lesson 1 Describing Motion Motion is everywhere. We can see it in the everyday activities of people, of vehicles in the road, in the plants that sway and even in the smallest particles – the atoms that vibrate and jostle. We can move because of the contraction and expansion of our muscles. Everything moves. Even the things that are physically at rest are in motion (jostling molecules). Like in our case, even when asleep our lungs and heart continue to vibrate and pump. The number of times our heart beats in a minute is calledFig 1.1 The Heart our heartbeat. The normal heartbeat is equal to or less than 100 times per minute for adults. A heartbeat consists of 2 parts: diastole and systole. During diastole,the heart muscle relaxes, allowing blood to flow into the atria and ventricles. During systole,the ventricles contract pumping blood to the different parts of the body. The “lub dub” soundof the heartbeat that is heard in an instrument called stethoscope is caused by the closing of 5

the heart valves. They move with respect to or relative to certain objects like the sun, thestars and the moon. This means that motion is relative. Motion is very easy to recognize but has been very hard to describe. There areseveral physical quantities that can quantitatively describe the motion of objects. Some ofthem are distance and displacement.Distance vs. Displacement Distance is usually described as the total path length. It is the length between anidentified reference point and a designated position. It is a scalar quantity, which means thatdistance is expressed as magnitude only. It is expressed in units such as meter, kilometer,feet and the like. However, the standard (SI) unit for distance is meter. Here are someexamples of distances.Example 1.1 The distance between the tower and the boy is 10 m. This means that thelength between the reference point (the tower) and the identified position (boy) is 10 m. d = 10 mIdentified position Reference pointExample 1.2. The distance between the house and the church is about 5 m. This meansthat the total path length between the reference point (the house) and the identified position(church) is the sum of the different lengths (1m, 0.5m, 2m, and 1.5m), which is equal to 5 m. 1.5 m 2m 0.5 m 1m 6

REMEMBER THIS! Displacement, on the other hand, is theDistance total path length measure of how far an object has moved in a – symbol: d particular direction from its original position. This – SI unit: m is usually described as the length between the – initial and the final position or the change inTotal Distance position including the sign of the change. – Sum of different length of a given Displacement is a vector quantity. This means path that displacement is expressed as magnitude with the corresponding direction. It is usuallygiven a symbol d, which is a symbol for a vector quantity. It is also expressed in units suchas meter, kilometer, feet and the like. However, the standard (SI) unit for displacement ismeter. Here are some examples of displacements.Example 1.3. When the boy move from point A to point B, the distance of the boy from thetower is 10 m but the boy’s displacement from the tower is 10 m, W. This means that thelength between the initial position of the boy (point A) and the final position of the boy (pointB) is 10 m moving toward the west. In symbols; d = 10 m ,W d = 10 m Point B Point AExample 1.4. However, if the boy who started from the tower (point A) moved to point Bthen went back to point A (tower), then the boy’s initial position is point A (tower) while hisfinal position is still point A (tower). Then the length between the initial and the final positionis 0 m. Therefore, his displacement from the tower is 0 m. d = 0m d = 10 m Point B Point ADisplacement can also be described as the difference between two distances. 7

d1 = 10 m d2 = 10 m d = ∆d = d2 - d1 = (10 m) – (10 m) = 0m What you will do Activity 1.1 Measuring DisplacementObjective: To measure and determine displacement of a 10-centavo coin or a washerMaterials: washer or 10 centavo-coin, centimeter ruler paperProcedure: 1. Place a washer or a 10-centavo coin on the number line with the center of the washer or the 10-centavo coin at the position marked zero. 2. Draw a circle around the inside of the washer or the 10-centavo coin. 3. Mark the center of this circle with the letter I for the word \"initial\" position of the washer. 4. Move the center of the washer 5.0 cm to the right. Label this circle F for the \"final\" position of the washer. 0Guide Questions:1. What was the initial position of the washer?2. What is the final position of the washer?3. What is the distance traveled by the washer?4. What is the displacement of the washer?5. Which of the underlined quantities (final position, distance traveled, and displacement) are numerically equal? Key to answers on page 32 8

Speed and Velocity The idea of rate is also a good tool in the description of motion. A rate is a quantitydivided by time. It tells how fast something happens, how much something changes incertain amount of time. Speed is one example of a rate. It is a measure of how fastsomething is moving. It is also known as the rate at which distance is covered. In symbols; ν =d t where: v = speed d = distance covered t = time of travel d The SI units used for speed is m/s, km/h, m/min, etc.νt Here’s a good way of remembering this equation and all other equations that can be derived from the given equation. If you need an equation for distance then cover distance and write the symbol d in your paper. In such a case, ν and t are adjacent thus they are expressed as products.Hence, d = νtIf you want to have an equation for t, then cover t on the triangle and write the symbol t inyour paper, then since d is written above ν, then they appear as quotient. Thus, d and νmust be written as ratio. In symbols, t = d/νAre you now ready to take a look at the example below and see how we can use thedifferent equations?Example 1.5Elma Muros, the fastest female sprinter in the South East Asia can run along a 200-mdistance in 24.42 seconds. What is Elma’s speed?Given: d = 200 mRTF: t = 24.42 s v 9

Solution: ν= d t ν= 100m 10.49s ν = 9.53 m/sInstantaneous Speed and Average Speed Take a look at the dashboard of car or a jeep when Fig 1.2. Car Dashboardyou ride in one of them. The circular gauge encircled infigure 1.2 is called a speedometer. A speedometer is aninstrument that determines the instantaneous speed of avehicle. Does the speedometer always register thesame speed? At a red light, the car has a 0 km/h speed,and along the highway, its speed is probably 80 km/h.These individual speeds are known as instantaneousspeeds. Instantaneous speed is the speed of an objectat an instant.Fig 1.3 Car Dashboard Average speed, on the other hand, is the total distance covered by an object in a certain period of time. It is the representative speed of the whole course of travel. Using the sample of instantaneous speeds above, the average speed can be computed by getting the sum of all the individual speeds and dividing the sum by the number of instantaneous speeds. In the case above, the average speed is about (80 km/h + 0 km/h)/ 2, 40 km/h. On the other hand, a much easier way of determining the average speed is to look at the odometer. An odometer like the one encircled in figure 1.3 is an instrument that informs the total distance traveled by the vehicle. Average speed is the ratio of the total distance traveled and the total time of travel. In symbols, ν= dT tTwhere:vave = average speeddT = total distance traveledtT = total time of travel Our blood, which flows from one part of the body to another, has an average speed of about 0.6 m/s 10

VelocityIn everyday situations, speed and velocity are just the same. They only describe howfast an object moves. In physics, however, they are a lot different. Velocity is a speed in agiven direction. It is known as the distance traveled in a particular direction in a given timeinterval. In symbols,(3) ν = d, dir t intwhere: ν = velocityd, dir = distance in a given directiontint = time interval More often than not, d + dir which means distance in a given direction is also calleddisplacement. Both speed and velocity are expressed in units such as m/s, km/h, m/min,etc. Thus, ν= d t intwhere: v = velocity d = displacement tt = time intervalExample 1.6.Karen drove to the city to pick up a friend. She went 280 km east in about 9.6 hours.Calculate her velocity.Solution: 1. Given Required to Find d = 280 km, E vave tt = 9.6 hr1. Equation: vave = d2. Solution: vave = vave = t int d t int 280km, E 9.6hr 11

What you will do Activity 1.2 Determining Average Speed and Average VelocityObjective: A. To determine the average speed and the average velocity of a skier B. To differentiate average speed and average velocityProcedure: 1. Below is a diagram of a man who is skiing. Ski is a sport that is done on places where we have snow.Use the diagram to determine the average speed and the average velocity of the skierduring these three minutes.Results: Distance Distance Distance Total Total Average (0-1) (1-2) (2-3) Distance Time Speed min min min 100 m 3 min Initial Final Displacement Total Average Velocity Position Position (0-3) min Time AD 3 min 12

Guide Question: 1. Differentiate average speed and average velocity. Key to answers on page 32Acceleration Imagine yourself driving your bicycle along the road when suddenly a man crossesthe road. What would you do? Definitely you step on the brake! What happens to the bicycleas you step on the brake? When an object changes its velocity the object is said toaccelerate. Acceleration is a measure of how fast the velocity changes with respect to time.This means that a body accelerates whenever there is a change in speed; a change indirection, or a change in both the speed and direction. Acceleration is expressed in unitssuch as m/s2, km/h2, m/min2, etc. Blood flow also exhibits acceleration. When the heartpumps the blood is pushed away from the heart. The sudden surge or push to the bloodmakes the flow of the blood change in speed or direction. a= ∆ν t intwhere: = acceleration a = change in velocity ∆v = time interval tintor a= νf −νi t int final velocitywhere: = initial velocity vf = vi 13

What you will do Self-Test 1.1Oops! Before you go on, try this one!A. Direction: Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1 Which of the following is an example of acceleration? A. 5 m/s B. 5m/s2 C. 5 km/h D. 5 m/min2. Suppose you are in a car that is going around a curve the speedometer reads a constant30 km/h. Which of the following is NOT true? A. Your speed is constant B. Your velocity is constant. C. You and the car are accelerating3. Which of the following exhibits acceleration? A. A body at rest B. A body at uniform speed C. A body with uniform velocity D. A body moving with constant speed in a circle4. Which of the following instruments measures the distance traveled by a vehicle? A. Odometer B. Manometer C. Speedometer D. Anemometer5. Which among the following is an example of velocity? A. 50 km/h B. 40 km/h C. 50 mi/h D. 40 mi/h, EB. Direction: Write ”A” if the situation shows an accelerated motion and write “B” ifthe situation shows that the motion of the object is not accelerated. 1. The initial velocity of a boy in a bike is about 5 km/h E while his final velocity is about 7 km/h E. 2. A boy on his bike moves around a curve with a constant speed of 5 km/h. 3. A man initially running at 7 km/h E, moves west at the same speed of 7 km/h. 14

4. A boy initially running at around 3 km/h suddenly stops because of a truck.5. A girl initially sitting on a bench stood up and started running. Key to answers on page 33Lesson 2 Linear Motion Take a look at the parachuters. Are they falling? Are they moving horizontally? Motion comes in 2 forms: linear motion and curvilinear motion. Linear motion refers to the movement of an object along a straight path. Examples of these are vehicles and other objects with a constant acceleration and freefall. Curvilinear motion is the motion of bodies along curved paths. Projectile and object moving along circular paths are some examples.Fig 2.1. ParachutersUniformly Accelerated Motion If a vehicle maintains a constant or a uniform change in its velocity in a given timeinterval along a straight line, then the vehicle is said to have a constant acceleration. Itsmotion is known as uniformly accelerated motion. This constant acceleration could bederived using the equation: a= vf − vi t int 15

Free Fall Are there waterfalls in your vicinity? How would you describe them? The water is usually called a freely falling body. Its motion is known as free fall. Freefall is an example of a uniformly accelerated motion. In such a motion, the only force acting on the body is the gravitational pull of the earth which is also called the earth’s gravity. For an object in freefall, the acceleration is a constant popularly known as gravitational acceleration or acceleration dueFig 2.2 Water falls to gravity also directed downward (-g). On the earth’s surface at sea level the exact magnitude is 9.8 m/s2. Ten(10 m/s2) is used, however, for easier analysis of motion. This means that the velocity of anobject in freefall changes by 9.8 m/s or 10 m/s every second of fall. If an object is dropped a certain distance from the ground, then its motion is alsoknown as freefall. In such a case the initial velocity of the object dropped with respect to thevertical axis is zero (0). νi = 0 Did you know that the concept of freefall helps determine our reaction time? Reactiontime is the time it takes for the information sent to the brain to travel to the different parts ofthe body for execution. Here’s one way of determining your reaction timeWhat you will doActivity 2.1 My reaction timeHere’s a great task that you can do.1. Ask a friend to help you.2. Have a 12-in ruler and let your friend hold its tip for you.3. Position your hand on the zero-mark of the ruler but take extra care not to touch the ruler.4. When your friend releases the ruler, catch it with your fingers initially positioned at the zero-mark.5. Note the distance covered from the zero mark to where your fingers are when you caught the ruler. This represents the distance covered.6. Determine your reaction time using the equation: t = √(2d)/g where: tr = reaction time d = distance covered g = acceleration due to gravity (9.8 m/s2) 16

Another example of a freely falling body is an object thrown vertically downward. Forconvention, the initial velocity of such case is always expressed as a negative value(downward, -νi). νi = -ν Objects thrown vertically upward are also considered freely falling bodies. Whetherthe object goes up or goes down the only force acting is the pull of earth’s gravity. Theinitial velocity of the object is only a result of the initial force exerted by the launcher. What you will do Self-Test 2.1 Answer the following very carefully. Write your answers on a separate sheet. A ball is thrown vertically upward. a. What is the acceleration of the ball after 1 s? ___________ b. What is the acceleration of the ball at its maximum height? _____________ c. What is the velocity of the ball at the top of its path? _____________ d. If the ball is thrown with an initial velocity of 50 m/s, what is the final velocity of the ball at a point at the same level as when it was thrown? ___________ e. What force was exerted on the ball 1 second after it was thrown? ___________ f. What exerts this force? _____________ g. What is the acceleration of the ball 10 seconds after being thrown up? ___________ h. If the ball took 5 s to reach its maximum height, how long will the ball go back to where it was initially launched? i. What is the acceleration of the ball at the top of its path? ___________ j. What is the speed of the ball at the top of its path? _____________ Key to answers on page 33 17

Lesson 3 Curvilinear MotionProjectile Motion When the player hits the “Sepak”, the motion of the “Sepak” is called projectile motion. The “Sepak” itself is called projectile. The “Sepak” will follow a parabolic path called trajectory especially if air resistance is negligible. Two coordinates are usually used to describe projectile motion: horizontal and vertical axes. The horizontal distance traveled by the projectile is called the range. While the vertical distance, that is, the distance from where it was launched toFig 3.1 Sepak Takraw the top most point of its path is called its height.Players Examples of projectiles are cannon ball launched by acannon, golf ball hit by a golfer, and an ice skater jumping over some barrels. Usually, astrong, abrupt force initiates the motion of a projectile. Following this force, the projectilemoves through the air and is influenced only by the earth’s gravitational force pulling it downand by air resistance. If the effect of air resistance is ignored, equations in free fall arereadily used to analyze the motionof a projectile – how high it willtravel, how far it will go and so on.A remarkable thing to note isthat the same range is obtainedfrom two different projection angles– complementary angles. An objectthrown into the air at an angle of75o, for example, will have thesame range as if it were thrown atthe same speed at an angle of 15o. RangeAn object thrown at 60o will havethe same range as when the objectis launched at 30o. As you can see, Fig 2.4 Angle of Projection vs. Rangewhen we get the sum of 75o angleand 15o angle, 60o angle and 30oangle, in both sets we would obtain a 90o angle. This means that 75o angle and 15o angleare called complementary angles. Similarly, 60o angle and 30o angle are alsocomplementary angles. Thus, complementary angles (angles whose sum is equal to 90o)would result to equivalent range. For smaller angles, object remains in the air for a shortertime. A maximum range is attained when an object is launched 45o from the horizontal. 18

Projectile motion is a very helpful and practical concept in Physics. For example, if there are floods and rescuers could not reach the place, a rescue plane is usually used to drop a package of emergency rations to the victimsFig 3.2 Plane to the rescueCircular Motion Have you experienced riding the merry-go-round? Which moves faster – the horse near the outside rail or the horse near the inside rail? Have you tried swinging a tin can overhead? When the string breaks, how does the can move? Does it move directly outward or does it move tangent to the circle? You and your friends would probably answer theFig 3.3 Merry-go-round questions differently. Some may chose the horse near the inside rail, while others the horse near the outside rail. That’sbecause some of you maybe are thinking about linear speed while others rotational speed. All objects that turn around on axis located within the object is said to be rotating.When an object turns about an external axis the rotational motion is called revolution. Linear speed is what we have been calling simply “speed” – the distance traveledper unit of time. A point outside the merry-go-round moves a greater distance in onecomplete rotation than a point inside it. Linear speed is thus greater on the outside of arotating object than closer to the axis. Rotational speed (angular speed/velocity) refers to the number of rotations orrevolutions per unit of time. All parts of a rotating object share the same rate of rotation. Thisrate of rotation is usually expressed in revolutions per minute (RPM). A commonphonograph record, for example, rotates at 33.33 RPM. However, linear and rotational speeds are related. Linear speed is directlyproportional to rotational speed. This relationship is expressed in an equation as ν = rωwhere: ν = linear speed r = radius of the circular path ω = angular/rotational speed 19

In any rigid rotating system, all parts have the From the equation above, we notesame rotational speed. Linear speed varies as. that linear speed also depends on the distance from the center. The greater the it depends on the rotational speed and the radius the greater the linear speed if the distance from the axis of rotation. rotational speed is kept constant. At the very center (the axis of the rotating object) you have no linear speed but you still rotate.What you will doActivity 3.1 Whirling cansObjective: To observe circular motion.Materials: tin can, string, cutter or scissorsProcedure: 1. Tie a long string to a tin can. 2. Whirl the tin can at the end of the string above your head until you are able to make horizontal circles. 3. Observe how the tin can moves while traveling along the circular path. 4. Observe how your hand holding the string tied to the tin can behave. What do you notice? Did you notice that you kept on pulling the string to maintain itscircular motion? This force that causes the tin can to follow a circular path is calledcentripetal force. Centripetal force means “center-seeking” or towards the center. In thecase of the can your hand exerts the centripetal force. 20

Gravitational force is the centripetal force exerted on moon byearth to maintain an almost circular path. The same centripetal force(gravitational force) is responsible for keeping the planets in their orbitabout the sun. And in an atom, the electron orbits the nucleusbecause of the electrical force between them. Centripetal force depends on the mass (m), the tangentialspeed (ν), and the radius of curvature (r) of the circularly movingobject. In symbols; Fc = mv 2 rwhere: Fc = centripetal forceFig 3.4 (upper) Solar System m = mass(lower) Atom r = radius of curvature ν = tangential speed What you will do Activity 3.2 Whirling cansObjective: To observe circular motion.Materials: tin can, string cutter or scissorsProcedure: 1. While whirling the tin can, cut the string. 2. Observe the motion of the can while it moves away from the circular path. If the string breaks how does the tin can move? In the early years people thought thata “center-fleeing” force counteracts the centripetal force. This is known as centrifugalforce. It is believed that centrifugal force pulls the can from its circular path. But the fact isthat when the string breaks, the can goes off in a tangent, straight-line path because noforce acts on it! Similarly, if you are in a car that rounds a sharp corner to the left, you tendto pitch outward to the right – not because of an outward force but because of the absenceof centripetal force holding you in circular motion (as a seatbelt provides). 21

Lesson 4 Physics and Transportation Which among the following vehicles do you often use? Does it make traveling more convenient or it is better to travel on foot. Which do you prefer? Have you ever tried riding on one of the following forms of transportation? Do youhave any idea what forms of transportation were used by your ancestors like yourgrandmother or great grandmother?Brief Account of Transportation No one basically knows when humankind first tamed the ox, the burro, the horse and the carabao. All we know is that we do move from one place to another to trade using our feet. American Indians shipped copper, iron oxide and other valuables from Minnesota to Alabama on foot over “forest highways” or downriver. 22

The principal innovation on land transportation wasthe construction of roads where horses and riderscould keep a message moving at the speed of abouttwo hundred miles a day. Freight was carried by acamel, an elephant, a burro or an ox. Humanporters, on the other hand, carried cargos in China.In the Philippines, the most famous animal is thecarabao (kalabaw). It carries freight for its ownerwho is usually a farmer. Later, carriages wereconnected to these animals to improve the transportof goods and people.. In the Philippines, we call a horse-drivencarriage as “kalesa”. The kalesa or karitela wasintroduced during the 18th century. Spanish officialsand nobles used it as a chief means oftransportation. The illustrados, the rich Filipinos whohad their own businesses, used the kalesa not onlyfor traveling but as a means of transporting theirgoods.In 1867, the motorcycle was first invented. By the1880’s inventors tried very hard to make cars thatwould run well enough to use everyday. Since thecars replaced the horses and they ran on steam,they were called “Iron Horses” (steam-poweredcars). By 1890’s Europeans were buying and drivingcars by Benz.In the United States, automotive progress wasexemplified by the Old Motor Works, which massproduced 425 cars in 1901. In 1908-1927 HenryFord made the Ford Model T, which was ran bygasoline but costs much less than other cars. Itran well on dirty and bumpy roads. During this era,the Wright brothers invented the first heavier-than-air flight. 23

By the 1930’s transoceanic “flying boats” wereplying the ocean of the world at speeds greaterthan 150 miles an hour. Aircraft played adominant role in World War II. In the Philippines,the exotic jeepney is a post-war creationinspired by the GI jeeps that the Americansoldiers brought to the country in 1940’s.Enterprising Filipino salvaged the surplusengines and came out with a unique vehicle ofart. Then the jet passenger aircraft came. These were followed by supersonic transport. Not long after, the aerospace planes and spaceships came. In land transportation, one of the fastest vehicles is the bullet train or the MagLev (Magnetically Levitated) Trains. These are run by electricity, which also creates magnetism on both the rails and the road. Since both (rail and road) are like poles they then repel each other causing the train to be levitated or to be at a vertical distance (floating) from the road. In such a case, friction is decreased and the velocity of the train is increased.Today, there are many modes of transportationavailable in the Philippines. There are buses, taxi,jeepneys, the LRT (Light Rail Transit) and MRT(Metro Rail Transit). 24

What you will do Activity 4.1 Transportation: a historyObjective: To be able to complete the timeline below.Materials: worksheet, pencilProcedure:Complete the timeline illustrated below. You may do this by illustrating or identifying themeans or form of transportation according to the passage Brief Account ofTransportation. Timeline: ` Bicycle (1790) Motorcycle (1867) Ford Model T (gas-powered, 1908) Jeepneys (1940’s)Key to answers on page 34 MagLev Trains 25

What you will do Self-Test 4.1 Answer the following very carefully. Write your answers on a separate sheet. AB CD Which among the sets of vehicles would your prefer? Cite the advantages anddisadvantages of your choice. Key to answers on page 34 26

What you will do Activity 4.2 Physics of TransportationObjective: To identify basic physics principles that are related to transportation.Materials: worksheet, pencilProcedure: 1. Below is a picture of a vehicular accident. Identify as many physics concepts related to the accident as you can. Physics concepts: Key to answers on page 35 Understanding transportation accidents requires knowledge of the physics of movingbodies. Although these physical laws were discovered largely by Galileo and by Sir IsaacNewton in the 1600's, they were not always clearly understood. However, they really arevery simple, and depend only on a few key principles, which are familiar to you Newton'slaws of motion. Newton correctly explained the behavior of most objects. Transportationproblems require the application of Newton's Second Law, which states that theacceleration of a body is proportional to the force applied and inversely proportional to thebody's mass. Acceleration is not just \"gaining speed.\" Gaining speed is only one form ofacceleration. Braking or losing speed is another form, and it is usually expressed asnegative acceleration. Regardless of its type, acceleration requires force and is resisted bymass. 27

The law of friction states that the frictional force between two surfaces is proportionalto the \"normal\" force between them times the coefficient of friction. The normal force is theforce tending to press the surfaces together. In automotive situations, the normal force is theweight of the car on the tires. In normal operation, the frictional forces of the tires are themain acceleration and braking forces on an automobile, and those forces limit theacceleration, braking and cornering ability of the automobile. With these ideas and conceptsit is possible to predict the braking distance of an automobile when the speed and coefficientof friction with the road are known. Clearly, researches in physics brought about many inventions such as airbags,computerized fuel injection, electric sensors, General Pocket Radio Service (GPRS) and thelikes which are very helpful in upgrading both the efficiency of the engine and the safety ofthe passengers. Physics has helped transportation a lot. Let’s summarize 1. Distance is usually described as the total path length. It is the length between an identified reference point and a designated position 2. Displacement is the length between the initial and the final position. 3. Motion is relative. It is easy to recognize but hard to describe. 4. Rate, which describes motion, is a quantity per unit time. 5. Speed determines how fast an object moves. It is the ratio of the distance traveled and unit time. 6. Velocity describes how fast an object moves in a given time in a particular direction. 7. Acceleration is the change in velocity that happened in a period of time. 8. The two types of motion are linear motion and curvilinear motion 9. Uniformly accelerated motion and freefall are examples of linear motion. 10. Projectile and circular motions are examples of curvilinear motion. 11. A body is said to be moving in a uniformly accelerated motion when it maintains a constant acceleration throughout the motion. 12. The motion of a body on which the only force acting on it is the gravitational pull of the earth is known as freefall. 13. Projectile is a motion of an object when the only force acting on it is gravity. It includes both horizontal and vertical components of motion. 14. Circular motion occurs when there is a force exerted on an object that is directed towards the center. This force is known as centripetal force. 15. Linear speed is what we have been calling simply as “speed” – the distance traveled per unit of time. 16. Physics plays an important role in the advancement of transportation. 28

PosttestDirection: Choose the letter of the best answer. Write your answer on a separatesheet of paper1. Which statement is true? A. Speed indicates the direction of motion. B. Velocity indicates the direction of motion. C. Velocity measures the rate of motion only. D. The magnitudes of velocity and speed are always equal.2. A projectile is thrown 30o above the horizontal. What happens to its acceleration as itmoves upward? A. It decreases because its velocity is directed upward B. It increases because its velocity is directed upward C. It decreases because its velocity is decreasing D. It remains the same3. Which of the following is an example of acceleration? A. 5 m/s B. 5m/s2 C. 5 km/h D. 5 m/min4. Suppose you are in a car that is going around a curve and the speedometer reads aconstant 30 km/h. Which of the following is not true? A. Your speed is constant. B. Your velocity is constant. C. You and the car are accelerating.5. Which of the following exhibits acceleration? A. A body at rest B. A body at uniform speed C. A body with uniform velocity D. A body moving with constant speed in a circle6. Which of the following instruments measures the distance traveled by a vehicle? A. Odometer B. Speedometer C. Anemometer D. Manometer 29

7. When you throw a ball directly upward, it is accelerated ______________. A. at all times B. only as it falls C. during the instantaneous stop and during fall8. Which of the following instruments measures the instantaneous speed of a vehicle? A. Odometer B. Speedometer C. Anemometer D. Manometer9. Suppose an object is in freefall. The object falls each second _________________. A. with the same average speed B. with the same change in velocity C. with the same instantaneous speed D. with the same distance as in the second10. If you drop a feather and a coin at the same time in a vacuum tube, which will reach thebottom of the tube first? A. The coin B. The feather C. Both will reach the bottom at the same timeFor Nos. 11-16 the choices are: A. 0 m/s2 B. 9.8 m/s C. 9.8 m/s2 D. –50 m/s11. A ball is thrown vertically upward. At the top of its path what is its velocity?12. A ball is thrown vertically upward. At the top of its path what is its acceleration?13. A ball is thrown vertically upward, with an initial velocity of 50 m/s and caught back at the same level as when it was thrown. What is the velocity of the ball at that point?14. A ball is thrown vertically upward. What is its instantaneous speed at its maximum height?15. A ball is dropped from a cliff. What is the acceleration of the ball before it touches the ground?16. A ball is thrown vertically upward. What is the change in velocity of the ball after 1 second? 30

17. The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving toward the right. Do the blocks ever have the same speed? A. No. B. Yes, at instant 2. C. Yes, at instant 5. D. Yes, at instants 2 and 5. E. Yes, at some time during the interval 3 to 418. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks?19. A bowling ball accidentally falls out of the cargo bay of an airliner as it flies along in a horizontal direction. As observed by a person standing on the ground and viewing the plane as in the figure at right, which path would the bowling ball most closely follow after leaving the airplane?20. If you whirl a tin can on the end of a string and the string suddenly breaks, the tin can will A. fly directly away from you. B. fly off tangent to its circular path. C. fly directly toward you. D. spiral away from your hand. Key to answers on page 35 31

Key to AnswersPretest 11. D 1. C 12. D 2. B 13. B 3. C 14. C 4. A 15. D 5. C 16. A 6. C 17. D 7. C 18. D 8. B 19. B 9. B 20. C 10. ALesson 1Activity 1.1 1. 0 cm-mark 2. 5 cm-mark 3. 5 cm 4. 5 cm, right 5. distance and displacementActivity 1.2 Distance Distance Distance Total Total Average (0-1) (1-2) (2-3) Distance Time Speed min min min 180 m 140 m 100 m 420 m 3 min 140.00 m/min Initial Final Displacement Total Average Velocity Position Position (0-3) min Time 46.67 m/min, AD 140 m 3 min right* Velocity is the rate of displacement while speed is the rate of distance. 32

Self-Test 1.1A. B B. 1. B 1. B 2. D 2. A 3. A 3. A 4. D 4. A 5. 5. ALesson 2 e. Gravity f. EarthSelf-Test 2.1 g. 9.8 m/s2 h. 5 sa. 9.8 m/s2 i. 9.8 m/s2b. 9.8 m/s2 j. 0c. 0d. –50 m/s Choice CLesson 4 Advantages • faster than animalSelf-Test 4.1 driven • much more convenientChoice A • carry more load and passengers Advantages • no use of fuel or Disadvantages gasoline • use fuel and gasoline • lesser accidents • pollutes air Disadvantages Choice D • slow Advantages • tiring • very fast • very convenientChoice B • carry lots of load and passengers Advantages • no use of fuel or Disadvantages gasoline • high use of fuel • lesser accidents • pollution • faster than on foot Disadvantages • slow • tiring 33