Page 137 - Understanding NCERT Science 09

eventually come to rest? What happens to its energy
eventually? Is it a violation of the law of conservation of
energy?
16. An object of mass, m is moving with a constant velocity, v.
How much work should be done on the object in order to
bring the object to rest?
17. Calculate the work required to be done to stop a car of 1500
kg moving at a velocity of 60 km/h?
18. In each of the following a force, F is acting on an object of
mass, m. The direction of displacement is from west to east
shown by the longer arrow. Observe the diagrams carefully
and state whether the work done by the force is negative,
positive or zero.

19. Soni says that the acceleration in an object could be zero
even when several forces are acting on it. Do you agree with
her? Why?
20. Find the energy in joules consumed in 10 hours by four
devices of power 500 W each.
21. A freely falling object eventually stops on reaching the
ground. What happenes to its kinetic energy?

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