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WORK ENERGY POWER padlet.com/physiczdev/rnv4s9x0my3uxqte Made with serendipity Look at the images in the next few pages and make a guess readers  VISHNU SP FEB 21, 2022 11:03AM VISHNU SP APR 27, 2022 01:11AM WORK ENERGY POWER VISHNU SP MAY 09, 2022 06:31AM INDEX Introduction Work Examples of work Equation for calculating work Work against gravity Types of work Energy Types of energy Kinetic energy Equation for calculating KE Work energy principle Potential energy Equation for calculating PE Law of conservation of energy Power Equation for calculating power Questions Summary Concept maps Flip book QR Code References VISHNU SP APR 28, 2022 01:13AM VISHNU SP APR 27, 2022 01:11AM Introduction 1. Pulling a cart We use the term `work' in everyday conversation to mean many different things. We talk about going to work, doing homework, working in class. Physicists mean something very specific when they talk about work. In Physics we use the term work to describe the process of transferring energy from object or system to another or converting energy from one form to another. VISHNU SP APR 27, 2022 01:11AM WORK What is work? 

VISHNU SP APR 27, 2022 01:11AM Work done on an object is defined as the product of the magnitude of the force acting on the body and the displacement 2. Riding a bicyle in the direction of the force. VISHNU SP APR 27, 2022 01:11AM  W = Force x displacement          3. PUSHING A WALL W= F x s If a force acting on a body causes no displacement, the work done is 0. For example, pushing a wall. VISHNU SP APR 27, 2022 09:33AM VISHNU SP APR 27, 2022 09:34AM WORK S I UNIT OF WORK Work is defined as a force acting upon an object to cause a               W = F x s displacement. Force is measured in Newton (N) It is expressed as the product of force and displacement in the Displacement is measured in meter(m) direction of the force.     Work = Force X Displacement Work is done when a force produces motion             = 1N x 1m             = 1Nm Some motion shall be produced by work. For example,              = 1Joule(J)  if we push a wall and it doesn't move, so it is not work. VISHNU SP APR 27, 2022 09:14AM Another example is that if we push a desk it moves in the PROBLEMS direction of force, so we can say there is work. 1. A force of 10N causes a displacement of 2m in a body in its VISHNU SP APR 27, 2022 09:14AM direction. Calculate the work done by force 20J. FORMULA OF WORK Solution:       The work done by force = F x s                              = 10 N x 2m    = 20 J 2. How much force is applied to the body when 150 joules of work is done in displacing the body through a distance of 10m in the direction of force? Solution:                W = F x s

              F = W/s Radiant energy                   = 150/10  Nuclear energy                   = 15 N Ionization energy Elastic energy VISHNU SP APR 27, 2022 09:27AM Gravitational energy Thermal energy WORKOUT PROBLEMS Heat Energy VISHNU SP APR 28, 2022 12:45PM VISHNU SP APR 28, 2022 12:46PM ENERGY MECHANICAL ENERGY VISHNU SP APR 28, 2022 12:45PM KINETIC ENERGY VISHNU SP MAY 07, 2022 01:18AM What is energy? Energy is the ability to perform work. Energy can neither be created nor destroyed, and it can only be transformed from one form to another.  The unit of Energy is the same as of Work, i.e. Joules.  Energy is found in many things, and thus there are different types of energy. VISHNU SP APR 28, 2022 12:45PM DIFFERENT TYPES OF ENERGY VISHNU SP MAY 07, 2022 01:42AM VISHNU SP MAY 07, 2022 01:20AM k e vi 0:57 video Some other types of energy are given below: PADLET DRIVE Mechanical energy Mechanical wave energy VISHNU SP MAY 07, 2022 01:43AM Chemical energy Electric energy Magnetic energy

EQUATION FOR CALCULATING KINETIC ENERGY p e vi 0:58 video PADLET DRIVE VISHNU SP MAY 09, 2022 01:57AM VISHNU SP MAY 09, 2022 06:33AM WORK ENERGY PRINCIPLE EQUATION FOR CALCULATING POTENTIAL ENERGY The principle of work and kinetic energy (also known as the work-energy theorem) states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. VISHNU SP MAY 09, 2022 01:57AM VISHNU SP MAY 09, 2022 06:50AM POWER POINT PRESENTATION ON ENERGY VISHNU SP APR 28, 2022 12:45PM POTENTIAL ENERGY VISHNU SP MAY 07, 2022 01:43AM ENERGY Powerpoint presentation PADLET DRIVE VISHNU SP MAY 09, 2022 02:13AM LAW OF CONSERVATION OF ENERGY

     The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. This means that a system always has the same amount of energy, unless it's added from the outside. This is particularly confusing in the case of non-conservative forces, where energy is converted from mechanical energy into thermal energy, but the overall energy does remain the same. The only way to use energy is totransform energy from one form to another. VISHNU SP MAY 09, 2022 02:14AM VISHNU SP MAY 09, 2022 06:35AM CONCEPT MAP 1 - ENERGY EQUATION FOR CALCULATING POWER VISHNU SP MAY 09, 2022 02:19AM VISHNU SP MAY 09, 2022 06:34AM POWER MODEL QUESTIONS Power is the amount of energy transferred or converted per unit Question.1 time. In the International System of Units, the unit of power is Does work done depend upon the velocity of the body? the watt, equal to one joule per second. In older works, power is Answer. No. sometimes called activity. Power is a scalar quantity. Question.2 State the law of conservation of energy. Answer. It states that energy can neither be created nor destroyed. It can only change its form. Question.3 What will cause greater change in kinetic energy of a body? Changing its mass or changing its velocity ? Answer. Changing its velocity.

Question.4 Answer. List two essential conditions for work to be done. Given, displacement = 8 m, Answer. (i) A force must act and (ii) There should be Force = 7N displacement in the body. Now, Work done = Force x Displacement = 7 x 8 = 56 J Question.5 Question.16 When is 1 joule of work said to be done ?  Write an expression for the work done when a force is acting Answer. When a force of 1 newton acting on a body displaces it on an object in the direction of its displacement. in its own direction. Answer. Work done = Force x Displacement Question.6 What is the SI unit of work done and power ? Question.17 Answer. Joule and Watt.  A pair of bullocks exert a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in Question.7 ploughing the length of the field ? Find the energy in kWh consumed in 10 hours by a machine of Answer. power 500 W. Work done = Force x Displacement = 140 x 15 = 2100 J Answer. W = P x t = 500 x 10 = 5000 Wh – 5 kWh. Question.18 Question.8  What is the kinetic energy of an object? Write an expression for the work done in lifting a body of mass Answer. ‘m’ through a vertical height ‘h’. The energy possessed by a body by virtue of its motion is called Answer. Work done W = mgh, where g is acceleration due to kinetic energy. gravity. Question.19 Question.9  Write an expression for the kinetic energy of an object. When a book is lifted from a table, against which force work is Answer. done ? The expression is KE = 1/2 mv2, where ‘m’ is the mass and V is Answer. Work is done against the force of gravity. the velocity of the body. Question.10 Question.20 Will work be done by a man who pushes a wall ?  Define 1 watt of power. Answer. No. Answer. When a work of 1 joule is done in 1s, the power is said to be one Question.11 watt. What is the work done when the force acting on the body and the displacement produced in the body are at right angles to Question.21 each other ? A lamp consumes 1000 J of electrical energy in 10 s. What is its Answer. Zero. power ? Answer. Question.12 Given, W = 1000 J, t = 10 s, R = ? Is it possible that some force is acting on a body but still the Using p = W/t = 1000/10 = 100 W work done is zero ? Answer. Yes, when force acts at an angle of 90° with the Question.22 displacement.  Define average power. Answer. Question.13 When a machine or person does different amounts of work or What is the work done on a body moving in a circular path ? uses energy in different intervals of time, the ratio between the Answer. Zero, because force and displacement are total work or energy consumed to the total time is average perpendicular to each other. power. Question.23 Question.14  Define energy. Does every change in energy of the body involve work ? Answer. Answer. Yes. Energy is the ability of a body to do work. It is also defined as the capacity to do work. Question.15 A force of 7 N acts on an object. The displacement is, say 8 m, Question.24 in the direction of the force. Let us take it that the force acts  A body performs no work. Does it imply that the body on the object through the displacement. What is the work done possesses no energy ? in this case ?

Answer. It converts chemical energy into electrical energy. When a body does not perform any work, it never implies that the body has no energy. The body may have energy but still does Question.36 not perform any work, e.g., a book placed on a table has  Name one unit of power bigger than watt. potential energy but is not performing any work. Answer. A unit bigger than watt is kilowatt. Question.25 Question.37  What is the SI unit of energy?  When an arrow is shot from its bow, it has kinetic energy. Answer.The SI unit of energy is joule. From where does it get the kinetic energy? Answer. Question.26 A stretched bow possesses potential energy on account of a  Does a body at rest possess any kinetic energy ? change in its shape. To shoot an arrow; the bow is released. The Answer.No. potential energy of the bow is converted into the kinetic energy of the arrow. Question.27  What will happen to the kinetic energy of a body if its mass is Question.38 doubled ?  Name at least three commonly used units of energy. Answer. Its kinetic energy will be doubled. Answer. (i) Joule (ii) Erg (iii) Kilowatt hour. Question.28 Question.39  What will happen to the kinetic energy of a body if its velocity  Name the practical unit of power in engineering. is halved? Answer. Horsepower. Answer. The kinetic energy of the body will become one-fourth. Question.40 Question.29  Name at least six forms of energy. By how much will the speed of a body, of fixed mass, increase if Answer. its kinetic energy becomes four times its initial kinetic energy (i) Chemical energy ? (ii) Heat energy Answer. The speed is doubled. (iii) Light energy (iv) Electrical energy Question.30 (v) Sound energy  Can a body possess energy even if it is not in motion ? (vi)Solar energy Answer. Yes, it can possess potential energy. Question.41 Question.31  How many watt are there in 1 horse – power ?  Define potential energy. Answer. 746 watt. Answer. It is defined as the energy possessed by a body by virtue of its position or change in shape. Question.42  A light and a heavy body have equal kinetic energy. Which one Question.32 is moving fast?  Name the energy possessed by a stretched rubber band lying Answer. The lighter body is moving fast. on the table. Answer. Potential energy. Question.43  State the relation between kW h and joule. Define 1 watt. Question.33 Answer.  Give the SI unit of potential energy. 1 kW h – 1000 W h = 1000  Js-1  x 60 x 60 s = 3.6 x  106 J Answer. The SI unit of potential energy is.joule. 1 watt is the power of an agent which can do one joule of work in one second. Question.34  What do you mean by trans- formation of energy ? Question.44 Answer. It is the change of energy from one form of energy into  Is it possible that a body be in accelerated motion under a another form of energy. force acting on the body, yet no work is being done by the force? Explain your answer giving a suitable example. Question.40 Can energy be destroyed? Can energy be created ? Answer. Yes, it is possible, when the force is perpendicular to Answer. No, the direction of motion. The moon revolving round the earth under the centripetal force of attraction of the earth but earth Question.35 does not do any work on the motion of The moon.  A cell converts one form of energy into another. Name the two forms. Question.45 Answer.

 Define work. How is work measured ? When is work done by a (iii) A wind-mill is filling water from a well. force negative? (iv) A green plant is carrying out photosynthesis. Answer. Work is said to be done if force acting on an object (v) An engine is pulling a train. displaces it through a certain distance. (vi)Food grains are getting dried in the sun. It is measured as the product of force and displacement. (vii) A sailboat is moving due to wind energy. Work done is negative if force and displacement are in the Answer. opposite direction. (i) Work is done because the displacement of swimmer takes place in the direction of applied force. Question.46 (ii) If the donkey is not moving, no work is done as the  What is the work done by the force of gravity in the following displacement of load does not take place in the direction of cases ? applied force. (a) Satellite moving around the earth in a circular orbit of (iii) Work is done, as the displacement takes place in the radius 35000 km. direction of force. (b) A stone of mass 250 g is thrown up through a height of 2.5 (iv) No work is done, because no displacement takes place. m. (v) Work is done, because displacement takes place in the Answer. direction of applied force. (a) Zero, as the displacement in one complete revolution is zero. (vi)No work is done, because displacement does not take place. (b) Given m = 250 g = 0.25 kg, h = 2.5 m, g = 10 ms-2, W = ? (vii)Work is done because displacement takes place in the Now, W = FS = mg x h = 0.25 x 10 x 2.5 = 6.25 J direction of the force. Question.47 VISHNU SP MAY 09, 2022 02:58AM  Can there be displacement of an object in the absence of any force acting on it? Think; SUMMARY (Voice note) discuss this question with your friends and teacher. Answer. The answer is. both Yes and No. Yes, because when an object moves in deep space from one point to another point in a straight line, the displacement takes place, without the application of force. No, because force cannot be zero for displacement on the surface of earth. Some force is i essential. Question.48  A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not ? justify your answer. Answer. The person does not do work because no displacement takes place in the direction of applied force as the force acts in the vertically upward direction. Question.49 voice 2  Name the transformation of energy involved in the following 6:09 audio cases : (a) When a body is thrown upwards. PADLET DRIVE (b) When a body falls from the top of a hill. (c) When coal burns. VISHNU SP MAY 09, 2022 02:59AM (d) When a gas bums. (e) When water falls from a height. Answer. (a) Kinetic energy into potential energy. (fa) Potential energy into kinetic energy. (c) Chemical energy into heat energy. (cf) Chemical energy into heat energy. (e) Potential energy into kinetic energy. Question.50  Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’ (i) Suma is swimming in a pbnd. (ii) A donkey is carrying a load on its back.

voice 1 Science Class 9 Notes Work and Energy 1:32 audio PDF document PADLET DRIVE PADLET DRIVE VISHNU SP MAY 09, 2022 06:39AM VISHNU SP MAY 09, 2022 03:00AM CONCEPT MAP 2 ( Whole unit) REFERENCES VISHNU SP MAY 09, 2022 06:39AM https://www.google.co.in/books/edition/NCERT_Solutions_fo PDF NOTES r_Class_9_Science_Chap/Z3HpDwAAQBAJ? hl=en&gbpv=1&dq=work+energy+power+class+9+questions&prin tsec=frontcover NCERT Solutions for Class 9 Science Chapter 11 Work and Energy CBSE (सीबीएसई) NCERT (एनसीईआरटी) solutions for Class 9th Science Chapter 11 - Work and Energy from Bright Tutee provides access to all the exercises and questions and their answers. It helps you prepare the chapter from the examination point of view. The chapter focuses on topics including work, kinetic energy and rate of doing work. GOOGLE BOOKS VISHNU SP MAY 09, 2022 03:01AM https://www.google.co.in/books/edition/Frank_Modern_Certi ficate_Physics_Workboo/LQuQ5QT7RYcC? hl=en&gbpv=1&dq=work+energy+power+class+9+questions&prin tsec=frontcover Frank Modern Certificate Physics: (Workbook): (Part 2) GOOGLE BOOKS

VISHNU SP MAY 09, 2022 03:05AM ADDITIONAL VIDEOS https://www.youtube.com/watch?v=nUDpQVwlSCs WORK & ENERGY | Physics Animation Class 11 Physics Chapter 6 WORK, ENERGY AND POWER by EarthPen Animated Video Full NCERT Concepts by Dolphin Classes YOUTUBE YOUTUBE VISHNU SP MAY 09, 2022 03:05AM VISHNU SP MAY 09, 2022 06:42AM https://www.youtube.com/watch?v=kS-wQsUSHsY EXERCISE QUESTIONS WITH ANSWERS CBSE Class 9 Science - 11 | Work and Energy | Full Chapter | NCERT Animation by Shiksha House Official YOUTUBE VISHNU SP MAY 09, 2022 06:34AM VISHNU SP MAY 09, 2022 06:43AM https://www.youtube.com/watch?v=rf1BBWWe1Gk

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