Work and Energy : NCERT Exemplar

 

Multiple Choice Questions

Q.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

Sol. (c)

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Q.2 A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car

(a) Does not change

(b) Becomes twice to that of initial

(c) Becomes 4 times that of initial

(d) Becomes 16 times that of initial

Sol. (a)

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Q.3 In case of negative work the angle between the force and displacement is

(a) 0º

(b) 45º

(c) 90º

(d ) 180º

Sol. (d)

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Q.4 An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same

(a) Acceleration

(b) Momenta

(c) Potential energy

(d) Kinetic energy

Sol. (a)

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Q.5 A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 m s^–2)

(a) 6 ×10³ J

(b) 6 J

(c) 0.6 J

(d) zero

Sol. (d)

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Q.6 Which one of the following is not the unit of energy?

(a) joule

(b) Newton metre

(c) Kilowatt

(d) Kilowatt hour

Sol. (c)

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Q.7 The work done on an object does not depend upon the

(a) Displacement

(b) Force applied

(c) Angle between force and displacement

(d) Initial velocity of the object

Sol. d)

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Q.8 Water stored in a dam possesses

(a) No energy

(b) Electrical energy

(c) Kinetic energy

(d) Potential energy

Sol. (d)

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Q.9 A body is falling from a height h. After it has fallen a height h 2 , it will possess

(a) Only potential energy

(b) Only kinetic energy

(c) Half potential and half kinetic energy

(d) More kinetic and less potential energy

Sol. (c)