Q. 44.3( 171 Votes )

# Certain force acting on a 20 kg mass changes its velocity from 5 m s^{-1} to 2 m s^{-1}. Calculate the work done by the force.

Answer :

When the Velocity, *v* = 5 m/s

Mass, *m* = 20 kg

Then,

K.E. = *mv*^{2}

= × 20 × (5) 2

= × 20 × 25

= 250 J

When the Velocity, *v* = 2 m/s

Mass, *m* = 20 kg

K.E. = *mv*^{2}

= × 20 × (2) 2

= × 20 × 4

= 40 J

We know that,

Work done by force = Change in kinetic energy

= 250 - 40

= 210 J

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