Chapter 10

NCERT
Class 9
Science
Solutions
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?

Question:

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?

Answer:

Mass = m, Velocity = v

Then,

Initial K.E. = 1/2 mv2

Final K.E. after object comes to rest

Final K.E. = 0

Hence,

From the work-energy theorem

Work done = Change in kinetic energy

                  = Final K.E - Initial K.E

                  = 0 - 1/2 mv2

                  = - 1/2 mv2

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