Question

Certain force acting on a 20 kg mass changes its velocity from 5 m/s to 2 m/s. Calculate the work done by the force. (class 9th)

Answer 1

-210

v^-u^=2as

s=-21/20

w=Fs

w=-21/20*20*10

w=-210

Answer 2

Work done by the force=change in kinetic energy

=1/2mu2-1/2mv2

=1/2×20×(25-4)

=210J

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