Q4 of 33 Page 158

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.

When the Velocity, v = 5 m/s

Mass, m = 20 kg


Then,


K.E. = mv2


= × 20 × (5) 2


= × 20 × 25


= 250 J


When the Velocity, v = 2 m/s


Mass, m = 20 kg


K.E. = mv2


= × 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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