Science 4

4. On the Celsius scale, the boiling point of water is 100 o. What is the boiling point inthe Fahrenheit scale?a) 32 ºF b) 212 ºF c) 273 ºF d) 373 ºF5. The human blood has a temperature of 37 oC. What is this in K?a) 273 K b) 310 K c) 346 K d) 373 K6. Two bodies of different temperatures come in contact. Which of the following would NOT happen? a) Heat flows from a body of high temperature to a body of low temperature. b) The temperature of the hot body would increase. c) The two objects would have the same temperature after sometime. d) Particles in the colder object would move faster after sometime.7. One gram of steam at 100 oC causes a more serious burn than one gram of water at 100 oC because the steam a) is less dense. b) strikes the skin with greater force. c) has a higher specific heat capacity. d) contains more internal energy.8. A cup of hot coffee can be cooled by placing a cold spoon in it. Which of the followingmaterials would be best for this purpose? Assume all spoons have the same mass.(Specific heat: Al = 910 J/kg.K ; Cu = 390 J/kg.K; Fe = 470 J/kg.K; Ag = 234 J/kg.K)a) aluminum b) copper c) iron d) silver9. Evaporation cools a liquid because the a) slowest molecule tends to escape b) fastest molecules tend to escape c) pressure on the liquid decreases d) pressure on the liquid increases10. When vapor condenses into a liquida) it absorbs heat c) its temperature risesb) it evolves heat d) its temperature drops11. Fifty kJ of heat is added to a 20 kg block of ice at 0 oC. The amount of ice that meltsisa) 0.093 kg b) 0.15 kg c) 0.83 kg d) 2.5 kg12. If 10 kg of punch of specific heat 3.4 kJ/kg Co absorbs 340 kJ of energy, the changein temperature of the punch isa) 6 Co b) 8 Co c) 10 Co d) 12 Co 30

13. Expansion of a solid indicates that a) the number of particles in it increases. b) the space between its particles increases. c) the average velocity of particles increases. d) there is an increase in the average kinetic energy of its particles.14. A bimetallic strip consisting of copper and aluminum were subjected to a change intemperature and bent. Which figure shows the correct position of the bimetals? Refer to thetable below. Solid α ( X 10 -6/ Co) Aluminum 25 Brass 19 Brick 9 Iron 1215. Metals are good conductors of heat because a) they contain free electrons. b) their atoms are relatively far apart. c) their atoms collide frequently. d) their atoms are stable. Key to answers on page 37 31

Key to Answers Pre Test 1. b 2. d 3. b 4. c 5. c 6. a 7. b 8. c 9. b 10. b 11. b 12. c 13. b 14. b 15. c Lesson 1 Self-Test 1.1 1. kinetic energy 2. potential energy 3. gravitational 4. elastic 5. gravitational potential, kinetic Activity 1.1 3. a. The temperature of water increases as time passes. b. The temperature of water is 100 o C when it begins to boil. c. While the water is boiling, there is no change in the temperature. Activity 1.2 2. a. The temperature scales used in measuring temperature are the Celsius, Fahrenheit,and Kelvin scales. b. The freezing point of water at sea level is 0 o C or 32 o F or 273 K. c. Water boils at sea level at a temperature of 100 o C or 212 o F or 373 K. d. The temperature difference between the freezing and boiling temperatures is 100 o inthe Celsius scale, 180 o in the Fahrenheit and 100 in Kelvin scale. e. Changing temperature from Celsius to Fahrenheit Temperature in o F (TF ) = 180/100 TC + 32 or = 9/5 TC + 32 32

Changing temperature from Fahrenheit to Celsius Temperature in o C (TC = 100/180 (TF – 32) or = 5/9 (TF – 32) Changing Temperature from Celsius to Kelvin TK = TC + 273 Changing Temperature from Kelvin to Celsius TC = TK - 273Self – Test 1.21. Given: TC = 40 o C Find: TF Solution: TF = 9/5 TC + 32 = 9/5 (40) + 32 = 72 + 32 = 104 o F2. Given: TC = -84 o C Find: TF Solution: TF = 9/5 TC + 32 = 9/5 (-84) + 32 = -151.2 + 32 = - 119.2 o F3. Given: TF = 6152 o F Find: TC Solution: TC = 5/9 (TF – 32) = 5/9 (6 152 – 32) = 5/9 (6 120) = 3 400 o C4. Given: TF = 80 o F Find: TK Solution: a) Convert first the temperature from 0F to 0C TC = 5/9 (TF – 32) = 5/9 (80 – 32) = 26.66 o C b) Convert temperature to Kelvin TK = TC + 273 = 26.66+ 273 = 299.66 K 33

Activity 1.31. The movement of particles in hot object is faster than that in cold object.2. The temperature of the hot object is higher than the temperature of the cold object.3. When the two objects were placed in contact, the temperature of the hot object decreased while the temperature of the cold object increased.4. After sometime, the temperature of the two objects were the same.Self-Test 1.31. A person’s skin is warmer than the air around it during cold days.2. Our hand is warmer than the piece of ice.3. The flame of the candle is warmer than our hand.4. The general direction of heat flow between the person’s skin and the cold air around it is from the person’s skin to the cold air. The general direction of heat flow between the hand and the piece of ice is from the hand to the piece of ice. Between the flame and the candle, the direction of heat flow is from the flame to the hand.5. a.T = 30 o C T= 75 o C A Bb. Before the objects were placed in contact, the molecules in object B have greaterkinetic energy than the molecules in object C.c. The temperature of both objects after sometime will be the same.6. Energy transfers from an object of high temperature to an object of low temperature. Since the formerly hot object loses energy its molecules move slower than before. The molecules in the formerly cold object now move faster than before.7. Transfer of energy to an object will cause molecules in this object to have greater average kinetic energy, thus increasing its temperature.Lesson 2 Self- Test 2.1 1. Given: Energy = 34 Calories Find: Energy in calories, in kilocalories, in joules a. To convert energy in Calories to calories, convert first Calorie to kilocalorie. Use theconversion factor 1 Calorie = 1 kilocalorie Energy in kcal = 34 Cal x 1 kcal / 1 Cal = 34 kcalb. To convert energy in kcal to cal, use the conversion factor 1 kcal = 10 3 cal 34

Energy in cal = 34 kcal x 10 3 cal / 1 kcal = 34 x 10 3 cal or = 3.4 x 10 4 cal c. To convert energy to joules, use the conversion factor 1cal = 4.18 J Energy in J = 3.4 x 10 4 cal x 4.18 J / 1 cal = 14.212 x 10 4 J or = 1.4212 x 10 5 J 2. Given: Basal metabolic rate for women = 1 400 Calories / day Basal metabolic rate for men = 1 600 Calories / day Find: Basal metabolic rate for women in kcal /day, in calories / day Basal metabolic rate for men in kcal / day, in calories / day Solution: Basal metabolic rate for women in kcal /day = 1 400 Cal /day x 1 kcal / 1 Cal = 1 400 kcal /day Basal metabolic rate for women in cal / day = 1 400 kcal / day x 10 3 cal / 1kcal = 1 400 x 10 3 cal Basal metabolic rate for men in kcal / day = 1 600 Cal /day x 1 kcal / 1 Cal = 1 600 kcal Basal metabolic rate for men in cal / day = 1 600 kcal x 10 3 cal / 1 kcal = 1 600 x 10 3 cal Activity 2.1 B. 1. Aluminum melted the most paraffin. 2. Aluminum absorbed the most heat, so it has the most energy. 3. The temperatures of the three metals were the same before they were transferred to the paraffin. Activity 2.2 B. 1. It takes longer time to boil a kettleful of water than a cupful of water. 2. Energy transferred is greater in the kettleful of water than in a cupful of water. 3. A kettleful of water has a greater mass than a cupful of water. 4. The greater the mass of a substance, the greater is the energy transferred to it. Self – Test 2.2 1. It takes longer time to boil a kettleful of water than a cupful of water. 2. If it takes a longer time to heat a given substance, this indicates that the amount ofenergy transferred to the substance is greater. 3. The change in temperature of one cup of boiled water is equal to the change intemperature 1 kettle of boiled water. 4. The amount of energy transferred to a substance is directly proportional to its mass. 35

Activity 2.5 1. Given: m= 200 g ti = 0 oC tf = 0 oC Required: Q Solution: Q = mhf = 200 g X 80 cal/g Q = 16 000 cal 2. Given: m= 100g ti = 30 oC tf = 0 oC Required: Q Solution: Since the initial temperature of water is 30 oC, you need to determine first theenergy lost to change the temperature to freezing temperature which is 0 oC. Thendetermine the energy lost to completely freeze the water. Then add the two values to get thetotal energy lost. a) Energy lost to change temperature from 30 oC to 0 oC Q1 = mC∆t = 100 g X 1 cal/gCo X -30 Co Q1 = -3 000cal b) Energy lost to totally freeze the water Q2 = -mhf = 100g (80 cal/g) Q2 = -8 000 cal c) Total energy lost Q = Q1 + Q2 = ( - 3 000 cal ) + (- 8 000 cal) = - 11 000 cal Activity 2.6 1. The temperature of the solid in b is greater than the temperature of the solid in a. 2. The number of molecules in a is equal to the number of molecules in b. 3. The length of the solid in b is greater than the length of the solid in a. 4. The space between molecules in b is greater than the space between molecules in a. Activity 2.7 1. The thermal expansion of liquids is greater than the expansion of solids. 2. The volume expansion of gas is greater than those of solids and liquids. 36

Self- Test 2.7 1. Given: L = 6.0 m T1 = 25 o C T2 = 75 o C ∆t = 50 Co α = 1.7 x 10 -5 / Co a) ∆L = αL∆t = 1.7 x 10 -5 / Co x 6.0 m x 50 Co = 0.0051 m b) L2 = L1 + ∆L = 6 m + 0.0051 m = 6.0051 m Post Test 1. a 10. b 2. a 11. b 3. b 12. c 4. b 13. b 5. b 14. c 6. b 15. a 7. d 8. a 9. b -End of Module-ReferencesYoung, Hugh D. and R.G. Friedman. 2004, University physics (11th ed). Addison Wesley, San Francisco, CA: Pearson Education South Asia PTE Ltd.Hewitt, Paul. 2002, Conceptual physics: the high school physics program. Upper Saddle River, New Jersey: Prentice – Hall, Inc. 37

Module 15 Waves: Carriers of Energy What this module is about Few experiences are more relaxing than a day at the beach. The sight of waveswashing a shore, the sound of good music, and the feel of the sun’s rays help us forgetabout the pressure of examinations and other school projects. What might surprise you isthat the phenomenon of waves underlies all of those familiar experiences that will bediscussed in this module. In the previous modules, we have discussed the concepts of energy and how thisenergy is transferred in the form of work done. In most cases, energy is transferred bymechanical means. We also discussed that heating is another mode of energy transfer. Arethere other means of transferring energy?Another method of energy transfer is by wave motion. Module 16 will give you a detaileddiscussion on waves. You will study the following lessons in this module:  Lesson 1 - Nature of Waves  Lesson 2 - Types of waves  Lesson 3 - Characteristics of Waves  Lesson 4 - Properties of Waves What you are expected to learn After going through this module, you are expected to: 1. define the nature of waves; 2. explain how waves transfer energy; 3. differentiate wave pulse from wave trains; 4. distinguish between longitudinal and transverse waves; 5. explain the characteristics of waves; 6. solve problems relating frequency, wavelength, and speed of a transverse wave; and, 7. enumerate and explain the properties of waves. 1

How to learn from this module Here’s a simple guide for you in going about the module. 1. Read the instructions carefully. 2. Follow the instructions very carefully. 3. Answer the pretest in order to determine how much you already know about the lessons in this module. 4. Check your answers against the given answer key at the end of this module. 5. Read each lesson and do activities that are provided for you. 6. Perform all the activities diligently to help and guide you in understanding the topic. 7. Take the self-test after each lesson to determine how much you understood the topic. 8. Answer the posttest to measure how much you have learned from the lessons. 9. Good luck and have fun What to do before (Pretest) Encircle the letter of the best answer.1. Which of the following can be a medium for a wave? a. air b. water c. space d. all of the above2. A medium transfers a. air. b. matter. c. energy. d. molecules.3. An ocean wave is an example of a a. standing waves. b. stationary wave. c. transverse wave. d. longitudinal wave. 2

4. The maximum distance the molecules of a medium are displaced from their rest position is the a. speed. b. frequency. c. amplitude. d. wavelength.5. A large ripple tank with a vibrator working at a frequency of 30 Hz produces 25 complete waves in a distance of 50 cm. The velocity of the wave is a. 60 cm/s. b. 5/3 cm/s. c. 750 cm/s. d. 1500 cm/s.6. A source of frequency 500 Hz emits waves of wavelength 0.2 m. How long does it take the waves to travel 600 m? a. 3 s b. 6 s c. 12 s d. 60 s7. Which of the following is an example of longitudinal wave? a. blue light b. radio waves c. water ripples d. sound waves8. The bending of waves around the edge of a barrier is called a. reflection. b. refraction. c. diffraction. d. interference.9. Which of the following describes the effect of water waves passing into shallow water? a. wavelength increases, frequency increases, velocity increases b. wavelength increases, frequency unchanged, velocity increases c. wavelength decreases, frequency increases, velocity unchanged d. wavelength decreases, frequency unchanged, velocity decreases 3

The figure below represents a sea-wave that causes a small cork (Z) to rise up anddown through one complete oscillation every 4 seconds.Refer to this figure for questions 10-13 P Q RST Z1 meter 3 meters10. The amplitude of the wave is a. 0.5 m b. 1.0 m c. 1.5 m d. 3.0 m11. The wavelength of the wave is a. 0.5 m b. 1.0 m c. 1.5 m d. 3.0 m12. The horizontal speed of the wave is a. 4 m/s b. 12 m/s c. 0.25 m/s d. 0.75 m/s13. If the wave is moving to the right, after 4 seconds the cork (Z) will be at position a. P b. Q c. R d. S14. Four waves pass a certain point in one second with a speed of 80 cm/s. What is the wavelength? a. 0.5 m b. 10 cm c. 20 cm d. 0.05 cm 4

15. If the frequency of the wave is 2/s and its wavelength is 8 cm, what is the speed of the wave? a. 4 cm/s b. 6 cm/s c. 10 cm/s d. 16 cm/s16. A boat tied to a post is rocked by waves 12 m apart and with a speed of 3 m/s. What is the frequency of the wave? a. 4 waves/s b. 9 waves/s c. 15 wave/s d. 0.25 waves/s17. A wave with amplitude of 4 cm meets another wave of the same wavelength and amplitude. If their high parts meet, what is the amplitude of the resulting wave? a. 0 b. 4 cm c. 8 cm d. 12 cm18. Suppose the two waves in question #17 meet such that the high part of one wave meets the low part of the other. What is the amplitude of the resulting wave? a. 0 b. 4 cm c. 8 cm d. 12 cm19. Of the following characteristics of a wave, the one that is independent of the others is its a. speed. b. frequency. c. amplitude. d. wavelength.20. The higher the frequency of a wave is, a. the lower is its speed. b. the longer is its period. c. the greater is its amplitude. d. the shorter is its wavelength. Key to answers on page 19 5

Lesson 1 The Nature of Waves Whenever a medium is disturbed, there is a corresponding observable change in it.When you throw a small stone into the river, the water is disturbed and circular waves areformed. Consider a boy at the side of the river where a toy boat is floating at a distance notwithin the reach of the boy. The boy wants to move the boat. How will he do that? One-way to do it is to disturb the water to create waves. The waves will eventuallymove the boat. Based on what the boy did in the figure above, what is now your idea of a wave? Awave is a disturbance propagated through a medium in which energy is transferred. Themedium used in which energy is transferred is water, which is liquid in form. Waves do nottransmit matter, but they transmit energy. We have defined energy as the ability to do work and work as the product of forceand distance. Now consider a transverse pulse moving along a spring toward the personholding the far end. When the pulse reaches him/her, he/she feels a force pulling up ordown on his/her hand, and the force will move his/her hand slightly. Thus, it does work onhis/her hand. The person who started the wave pulse put energy into the spring, and thisenergy traveled in the form of a wave to the other end. Can you generate wave pulse and wave trains along a rope? Then try the succeedingactivity. 6

What you will doActivity 1.1 1. Get a piece of rope about 2 m long. Fix one end of a rope by tying it around a post or a rod. 2. Have a single disturbance in one end of the rope. What is formed? This time move that same end with a series of disturbances. What did you observe? The single disturbance made in a rope is called wave pulse while a series of disturbances are called wave trains. 3. How do you differentiate wave pulse from wave trains? 4. What is the medium used in this activity through which wave propagates? Key to answers on page 19What you will doSelf-Test 1.11. In Activity 16.1, how did you generate waves in a rope?2. What is transferred by waves from one place to another?3. What is necessary so that energy could be transferred by the waves produced by a rope? Key to answers on page 19 7