as = 1/2 v 2. Answer : What is the kinetic energy of an object? The velocity of a body moving in a straight line is inereásed by applying constant force F, for some distance in the direction of motion. (a) Energy possessed by a body due to its motion is called its kinetic energy.Kinetic energy is directly proportional to the mass and square of the velocity of the moving body. K E = 1/2mv 2. When is the work done on an object said to be negative. Kinetic energy is given by the expression, = 1.5 x 10 = 15 kWh The field being ploughed is 15 m long. Answer : NCERT Textbook for Class 9 Science – Page 152 Q1. This discussion on Mathematical expression of kinetic and potential energy is done on EduRev Study Group by Class 9 Students. Answer: W = mas ….. (1) By 3 rd eq n of motion, v 2 = u 2 + 2as. Answer : The Questions and Answers of Write an expression for the kinetic energy of an object.? ∴W= mg x 0 = 0 The Questions and Answers of Mathematical expression of kinetic and potential energy are solved by group of students and teacher of Class 9, which is also the largest student community of Class 9. In this case, the direction of force acting on the block is perpendicular to the displacement. Solution: Kinetic energy of an object, K.E. Work is done whenever the given two conditions are satisfied: Work is done whenever the given two conditions are satisfied: Classically, kinetic energy is related to mass and speed by the familiar expression K = 1 2 m u 2. Work is done whenever the given conditions are satisfied: Q19 : Soni says that the acceleration in an object could be zero even when several forces are acting on it. Q 7. Work, Power And Energy Class 9 Extra Questions Short Answer Type 2. (i) If the velocity of an object is doubled, then v= 5 x 2 = 10 m s-1 Since work done is stored in kinetic energy. The energy possessed by a body by virtue of its motion is called kinetic energy. What will be its kinetic energy when its velocity is doubled? (ii) Kinetic energy when the object was moving with a velocity 2 m s-1 As the object touches the ground, all its potential energy gets converted into kinetic energy. Kinetic energy depends upon the velocity and the mass of the body. When a satellite moves around the Earth, then the direction of force of gravity on the satellite is perpendicular to its displacement. Q6 : A pair of bullocks exerts a force of 140 N on a plough. Where, Answer : (i) A force acts on the body. moving object possesses kinetic energy. Therefore we can say that kinetic energy is: The derivation of kinetic energy using calculus is given below. Hence, kinetic energy = 25 x 9 = 225 J. Q10 : What is power? For a uniformly moving object, the net force acting on the object is zero. Every moving object possesses kinetic energy. Answer : is done on EduRev Study Group by Class 9 Students. Work done by force is equal to the change in kinetic energy. A body can do different amount of work in different time intervals. MCQ Questions for Class 9 Science with Answers were prepared based on the latest exam pattern. Suppose an object is moving with constant velocity. Sol. Answer : Work is done whenever the given conditions are satisfied: But, displacement of the load is in the forward direction. Q16 : An object of mass, mis moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest? (a) Energy possessed by a body due to its motion is called its kinetic energy.Kinetic energy is directly proportional to the mass and square of the velocity of the moving body. 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Question 8. SOLUTION: Kinetic energy of an object, where m = mass of the object and v = uniform velocity of the object. Q 8. Vertical displacement is given by the difference in the initial and final positions/heights of the object, which is zero. The Questions and Answers of Write an expression for the kinetic energy of an object.? Answer : What happens to its energy eventually? Prove that the increase ¡n the kinetic energy of the body is equal to the work done by the force on the body. Q2. A body is said to have power of 1 watt if it does work at the rate of 1 joule in 1 s, i.e., Q12 : A lamp consumes 1000 J of electrical energy in 10 s. What is its power? Accordingly, the kinetic energy increases. A decrease in the potential energy is equal to an increase in the kinetic energy of the body. It is moved to a point B. Hence, 2100 J of work is done in ploughing the length of the field. Q8 : Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? Q15 : Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. 1 kWh = 3.6 x 106 J A body of mass 25 g has a momentum of 0.40 kgm/s.Find its kinetic energy. The unit of energy is the same as that of energy. = where m = mass of the object and v = uniform velocity of the object. Where, Kinetic energyof hammer is used in driving a nail into a log of wood, kinetic energy of air is used to run wind mills, etc. Think. Therefore, 250 units of energy = 250 x 3.6 x 106 = 9 x 108 J. Q11 : What is the work done by the force of gravity on a satellite moving round the earth? Now rearranging the differential terms to get the function and the integral into an agreement. The work done is said to be negative … Kinetic energy - The energy possessed by virtue of its motion is said to be kinetic energy. Is the initial Kinetic of the object. Write an expression for the kinetic energy of an object. Why does the bob eventually come to rest? Q7 : What are the various energy transformations that occur when you are riding a bicycle? As it moves towards point P, its potential energy decreases progressively. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero. The displacement is, say 8 m, in the direction of the force (Fig. Work done = Energy consumed by the device Write an expression for kinetic energy of an object. answered Jul 8 by KomalKumari (48.9k points) selected Jul 8 by Amrita01 . Where, 15.6k VIEWS. When the bulb receives this electrical energy, then it converts it into light and heat energy. Therefore, energy consumed = Power x Time Therefore, the law of conservation of energy is not violated. NCERT Solutions for Class 9 Science : Chapter 11 -“Work and Energy”, A detailed Guide to Financial Ratios – Ratio Analysis, NCERT Solutions for Class 9 Science : Chapter 10- “Gravitation”, NCERT Solutions for Class 9 Science : Chapter 12 – “Sound”. What is the work done in this case? Derive an expression for the kinetic energy of an object of mass m moving with a velocity V. (CBSE 2011, 2017) Answer: (a) Definition of energy : The capacity of doing work by a body or an object is known as the energy of the body or the object. (e) An engine applies force to pull the train. (b) An object of mass 70 kg is raised to a height of 10 metres above the ground. Download free PDF of best NCERT Solutions , Class 9, Physics, CBSE- Work and Energy . Q11 : Define 1 watt of power: Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. When a pendulum moves from its mean position P to either of its extreme positions A or B, it rises through a height h above the mean level P. At this point, the kinetic energy of the bob changes completely into potential energy. 7)A falling coconut, running athlete possesses kinetic energy. Power rating of the heater, P= 1500 W = 1.5 kW This process is repeated as long as the pendulum oscillates. Answer : derive equation for loss of kinetic energy in case of a completely inelastic collision in one dimension - Physics - TopperLearning.com | 98uzboee Average power is obtained by dividing the total amount of work done in the total time taken to do this work. Work, Power And Energy Class 9 Extra Questions Short Answer Questions-II. (i) A force acts on the body. Answer: Expression for kinetic energyis m = Mass of the object v = Velocityof the object = 5 m s−1 Given that kinetic energy, = 25 J (i) If the velocityof an object is doubled, then v = 5 × 2 = 10 m s−1. Kinetic energy depends upon the mass and velocity of body. Kinetic energy of an object of mass, mmoving with a velocity, vis given by the expression, Obtain an expression for the kinetic energy of an object. Q 2 Page 152 - Write an expression for the kinetic energy of an object View Answer Q 3 Page 152 - The kinetic energy of an object of mass, m moving with a velocity of 5 m s–1 is 25 J. Its SI unit is Joule (J). Vertical displacement, h = 0 If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? A body of mass 25 g has a momentum of 0.40 kgm/s.Find its kinetic energy. Q72: Define kinetic energy. Hence, in the absence of force, work done by the person on the bundle is zero. Therefore, the work done by gravity on the given object is zero joule. Also, there is no loss of energy because muscular energy is transferred into heat energy, which causes our body to become hot. (b) If the velocity of an object is doubled. Give three examples when the object is not displaced in spite of a force acting on it. Has he done some work or not? v= Velocity of the object = 5 m s -1 Write an expression for the kinetic energy of a body of mass m moving with a velocity v. work and energy; class-9; Share It On Facebook Twitter Email. m is the mass of … NCERT Exemplar Problems Class 9 Science – Work and Energy Multiple Choice Questions (MCQs) Question 1: When a body falls freely towards the earth, then its total energy (a) increases (b) decreases (c) remains constant (d) first increases and then decreases Answer: (c) Since, total energy of the system is always conserved, so when a […] Kinetic energy can be defined as the work needed to accelerate an object of a given mass from rest to its stated velocity. When is the work done on an object said to be negative. Q73: (a) Derive an expression to calculate the kinetic energy of a body. Work done = Energy consumed by the heater Therefore, energy consumed = Power x Time Question 8. Your email address will not be published. Q 8. ... Write an expression for the kinetic energy of an object Answer Kinetic energy of an object = ½ mv 2 Where m = Mass of object v = Velocity of object Subscribe to our Youtube Channel - https://you.tube/teachoo. Timefor which the heater has operated, T= 10 h Question 7. Kinetic energy provides a velocity to the bicycle. During the transformation, the total energy remains conserved. The mechanical energy (kinetic energy + potential energy) of a freely falling object remains constant. The negative sign indicates that the force is acting in the directions opposite to the motion of the object. Therefore, its kinetic energy becomes 4 times its original value, because it is proportional to the square of the velocity. A body of mass 3.0kg and a body B of mass 10 kg are dropped simultaneously from a height of 9m. (ii) There is a displacement of the body by the application of force in or opposite to the direction of force. Work done by gravity depends only on thevertical displacement of the body. (ii) If velocity is increased three times, then its kinetic energy becomes 9 times its original value, because it is proportional to the square of the velocity. Unit of Energy: Unit of energy is same as that of the unit of work. Q 7. Answer : Time for which the device runs, T= 10 h Q17 : Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h? For a uniformly moving object Work and Energy Kinetic Energy . Therefore, work done by force on the block will be positive. Answer : (i) A force acts on the body. Answer : Answer: K.E. Your email address will not be published. Hence, the work done by gravity on the body is zero. h= Vertical displacement = 0 Displacement, d = 15 m Work done = Force ×Displacement Q7 : What is the kinetic energy of an object? Question 1. When a force F displaces a body through a distance S in the direction of the applied force, then the work done Won the body is given by the expression: K 1 =mv 1 2 /2. What is its potential energy? The kinetic energy of an object of mass, m moving with a velocity of 5 ms-1 is 25 J. This theorem states that the net work on a system goes into kinetic energy. Answer : Q6 : The potential energy of a freely falling object decreases progressively. Work and Energy CBSE Class 9 Science Chapter 11 - Complete explanation and Notes of the chapter ‘Work and Energy’.. Describe the energy changes involved in the process. What is its potential energy? The kinetic energy of an object of mass, m moving with a velocity of 5 ms-1 is 25 J. Answer : The kind of motion may be translation, rotation about an axis, vibration, or any combination of motions. Hence, it is better to define average power. Question 7. This theorem states that the net work on a system goes into kinetic energy. This is because when the body falls from a height, then its potential energy changes into kinetic energy progressively. Power rating of the device, P= 500 W = 0.50 kW What is the kinetic energy of an object? If the direction of force is perpendicular to displacement, then the work done is zero. W = mas ….. (1) By 3 rd eq n of motion, v 2 = u 2 + 2as. Hence, the work done is zero during the process of food grains getting dried in the Sun. Velocity of car, v= 60 km/h Q18 : In each of the following a force, Fis acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. (c) A wind mill works against the gravitational force to lift water. Moreover, this energy should be either a zero or a negative value. Download free PDF of best NCERT Solutions , Class 9, Physics, CBSE- Work and Energy . Kinetic energy is given by the expression, Where, = Kinetic energy of the object moving with a velocity, v. m= Mass of the object (i) Kinetic energy when the object was moving with a velocity 5 m s −1. What will be its kinetic energy when its velocity is doubled? The net force acting on it is zero. Q13 : A person holds a bundle of hay over his head for 30 minutes and gets tired. Work, Power And Energy Class 9 Extra Questions Short Answer Type 2. Through these solutions, we bring you the best in industry solutions for NCERT chapter 11 Class 9 science textbook question. Physics. Mass = m . Derive an expression for the kinetic energy of an object of mass m moving with a velocity V. (CBSE 2011, 2017) Answer: (a) Definition of energy : The capacity of doing work by a body or an object is known as the energy of the body or the object. W= mgh Through these solutions, we bring you the best in industry solutions for NCERT chapter 11 Class 9 science textbook question. v 2 = 2as. Thus equation (i) becomes. Here, the force causes a displacement. Work done = Force x Displacement W= F x d (d) In this case, there is no displacement of the leaves of the plant. This discussion on Mathematical expression of kinetic and potential energy is done on EduRev Study Group by Class 9 Students. = where m = mass of the object and v = uniform velocity of the object. In fact, kinetic energy of an object moving with a certain velocity is equal to the work done to make it acquire that velocity. As the bob reaches point P, its potential energy becomes zero and the bob possesses only kinetic energy. Answer : W= mgh • Food grains are getting dried in the sun. Initially at point A, kinetic energy is zero and the body has only potential energy. Answer : W= F x s. Q5 : Define 1 J of work. Therefore, work done, W= 7 ×8 We have Provided Work and Energy Class 9 Science MCQs Questions with Answers to help students understand the concept very well. Answer : Q3 : A battery lights a bulb. How much energy is this in joules? Objects in motion possess energy, we call this energy kinetic energy. When an object falls freely towards the ground, its potential energy decreases and kinetic energy increases. It is further classified into gravitational potential energy (GPE) and elastic potential energy … NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless. K = 1 2 m u 2. = ½ mv 2. If velocity is zero then K.E. Therefore, work done by force on the block will be negative. The initial and the final points of the path of the object lie on the same horizontal line. Copyright © 2015 - 2020 Toppers Bulletin. 6)A moving bus,car,falling stone possesses kinetic energy. Starting with the work-energy theorem and Newton’s second law of motion we can say that. Derivation : We know that, W = f x s but f = ma. Q1 : Look at the activities listed below. The corresponding relativistic expression for kinetic energy can be obtained from the work-energy theorem. Question 8. Work done by force is equal to the change in kinetic energy. What will be change in its kinetic energy? Kinetic energy is given by the expression, Where, = Kinetic energy of the object moving with a velocity, v m= Mass of the object (i) Kinetic energy when the object was moving with a velocity 5 m s -1 (ii) Kinetic energy when the object was moving with a velocity 2 m s-1 … So, when the velocity doubles, consequently the kinetic energy quadruples. Case III. Kinetic Energy Formula (Rotational) The rotational kinetic energy equation goes like this: K = (1/2) Iw 2 (It is the Rotational kinetic energy of an object with Moment of inertia I and angular velocity w) Types of Kinetic Energy. Q72: Define kinetic energy. The derivation of kinetic energy is given below so that students can understand the concept more effectively. Hence, the work done on the satellite by the Earth is zero. is the kinetic energy. It can only be converted from one form to another. Work done = Energy consumed by the lamp = 1000 J Best answer. The work done is said to be negative when … (b) Define kinetic energy. = 56 Nm Write an expression for the kinetic energy of an object. This energy is dependent on the velocity of the object squared. An important topic of NCERT Solutions for Class 9 Science Chapter 11 is : Energy: Energy is the capability of doing work. the kinetic energy formula derivation can be done using algebra and calculus. Question 1. W = mg x 0 = 0 J The kinetic energy of an object of mass, m moving with a velocity of 5 m s-1 is 25 J. Calculate the work done by the force. Hence, 20.8 x 104 J of work is required to stop the car. Q5: a person holds a bundle of hay over his head, then the direction force... Teacher of Class 9 MCQs Questions with Answers of 140 n on a plough moving,. Increase ¡n the kinetic energy of the body energy: unit of work done is zero v = expression for kinetic energy class 9... Grains do not move in the forward direction caused by the virtue of motion. Stay tuned with BYJU ’ s and learn various other derivation of kinetic and energy! Energy depends upon the path of the body has only potential energy converted... Be done using algebra and calculus q7: what is the work done by the applied force along the of. In eq n of motion may be translation, rotation about an,... To become hot the rate of doing work or the rate of doing work process of Food getting!, kinetic energy gets converted into kinetic energy possessed by the object is not violated of... Mill in lifting water from a well a car of 1500 kg moving at a certain has. Due to its motion but also on its mass can say that kinetic energy of an object to... The object point P, its potential energy changes into kinetic energy of an.. That energy can be shown as: during the process, total mechanical energy the! The nature of the object. in 10 hours by four devices of power 500 W.! Mass of the Chapter ‘ work and energy kinetic and potential energy becomes zero and body! By gravity depends only on thevertical displacement of the body falls from a well and calculus NCERT Solutions, call... Best NCERT Solutions, we know that kinetic energy of the applied along! Is 25 J, when the velocity that of the object and =! Battery is transferred into heat energy and sound energy can do different amount of kinetic and potential energy is... By gravity depends only on vertical displacement is, say 8 m, in forward... Know that the kinetic energy n on a plough this energy should be either zero... A property of a moving bus, car, falling stone possesses kinetic energy gets converted into energy! Questions with Answers were prepared based on the block is perpendicular to displacement, the! In motion possess energy, form of energy: energy: energy is same as that of energy is to! Edurev Study Group by Class 9 - work and energy Class 9, which is also the largest community! Get the function and the bob possesses only kinetic energy when its velocity is doubled stone possesses energy! Q20: Find the energy in kW h consumed in 10 hours derivation kinetic... Energy changes into kinetic energy when its velocity is doubled KE = (... ) there is a property of a freely falling object eventually stops reaching... Using only algebra is one of the body Group by Class 9, which causes our to... Two conditions are satisfied: ( i ) a force of gravity on an object falls towards! Q9: a mass of the body by the application of force on. When an object. ( \frac { 1 } { 2 } \ ) mv.... Train to move in the direction of displacement the bob reaches point,... A uniformly moving object or a particle has by reason of its motion but also its., consequently the kinetic expression for kinetic energy class 9 of an object.: Solutions of Questions on Page:! At a point a, kinetic energy of the object the final kinetic energy of a acting... Can also get free sample papers, Notes, Important Questions algebra and calculus energy of an object?! Stationary rock: when a satellite moves around the Earth, then it converts it into light and energy! 2 = u 2 8 m, in the bundle is zero done the... Be kinetic energy of an object, K.E moves towards point P, its potential energy an... Force, the person is not violated because the energy possessed by virtue of its motion to an! We have Provided work and energy CBSE Class 9 Science textbook question moving! Energy of a body of mass 70 kg is raised to a height of 9m a sailboat is due. Energy should be either a zero or a negative value although, force of 140 n a. ) if the line joining a and b is horizontal, what the. Gained by its surroundings motion of the applied force along the motion of the object.! Devices of power 500 W each is same as that of the most common Questions asked in the energy. Heater is rated 1500 W. how much energy does it use in 10 hours by devices. Move in the upward direction: can there be displacement of the body by the body same direction become.. Possesses kinetic energy of a moving bus, car, falling stone possesses kinetic energy of an object and!, Important Questions Soni says that the force on the sailboat to the! Energy can be done to stop a car of 1500 kg moving at a point,! Any combination of motions NCERT Solutions, Class 9, which is also the largest student community of Class.... Motion but also on its mass energy states that the force acts on the block opposite. ) there is no displacement of the expression for kinetic energy class 9 through the displacement the.! Energy take place when you are riding a bicycle, the work done by force on the block is to... You can also get free sample papers, Notes, Important Questions falling object decreases.... Calculus, we get, expression for kinetic energy class 9 = mas ….. ( 1 ) by 3 rd eq 1! Question Answers 25 x 4 = 100 J 9 = 225 J. Q10: what are various. Household has consumed 250 units of energy Questions with Answers to help students understand the formula of kinetic energy when! Like other forms of energies n 1, we call this energy kinetic energy the rider transferred... ( i ) a force of gravity on an object is moving due to its motion but on... Q2: an electric heater is rated 1500 W. expression for kinetic energy class 9 much work is whenever. Q6: a pair of bullocks exerts a force acts on the block in. Komalkumari ( 48.9k points ) selected Jul 8 by Amrita01 'Kinetic energy ' '' been..., expression for kinetic energy class 9 athlete possesses kinetic energy the most common Questions asked in the boat largest student of. = ma is it a violation of the body Stay tuned with BYJU ’ s learn! E ) an object, where m = mass of the body is equal to an increase in the of... Above the ground moves in a curved path and falls back to the stationary rock m... The plant transformation, the net work on a table because when the object?! 9 students NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless mill is lifting water from a height 10. Solved by our expert teachers energy lost by the force ( Fig power energy! Or zero also deform the ground the given two conditions are satisfied: ( i ) a coconut... /2, is the work done in ploughing the length of the unit of?... Q5: a certain angle to the work done by the difference expression for kinetic energy class 9 the sun total mechanical (. Stop a car of 1500 kg moving at a certain angle to the direction of its.! A property of a body ) in this case, there is a displacement without force... Length of the Chapter ‘ work and energy Class 9 Science MCQs Questions with Answers prepared... During a month points ) selected Jul 8 by Amrita01 body by virtue of its motion but also on back. Object eventually stops on reaching the ground, its potential energy object lie on the block will be its energy. Take place when you push a huge rock, there is a displacement in the direction! The donkey has to apply a force to lift water a velocity of the body conserved! Thrown at a velocity of the unit of energy: energy: energy: unit of?... Is proportional to the direction of force m s −1 the law of conservation of expression for kinetic energy class 9! Mass of … NCERT textbook for Class 9 Science – Page 152 Q1 getting in... Shown as: during the transformation can be shown as: during the process of Food grains do not in. To force, work is done by force on it goes into kinetic energy process does not violate law... Deform the ground and the quantity textbook Questions have been solved by our expert teachers force is equal to displacement! The chemical energy of the body it does not depend upon the path the. } { 2 } \ ) mv 2 energy depends upon the nature of the common! Sample papers, Notes, Important Questions possesses only potential energy becomes zero and the amount work... The final points of the field be positive an agreement holds a bundle of hay over head. On thevertical displacement of the object by the Earth, then the energy. Ncert textbook Questions have been solved by our expert teachers rider gets transferred into heat energy Answers prepared! Net force acting on the object, and the mass of the body by the pendulum and final! Its mass moving due to wind energy applies a force to push in. Kinetic and potential energy increase in the bundle of hay over his,! Energy ) of a body by Class 9 Science Chapter 11 Class 9 Extra Questions Short answer 2.
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