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)

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)

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)

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)

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)

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)

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)

Q.8 Water stored in a dam possesses

(a) No energy

(b) Electrical energy

(c) Kinetic energy

(d) Potential energy

Sol. (d)

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)


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