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.

Answer 1

Mass of an object m= 20 kg,Initial velocity u = 5m/sand final velocity v = 2m/s

.·. Initial kinetic energy of object E1 = ½ mu²= ½ x 20 x (5)² = 250 J

And final kinetic energy of object E2 = ½ mv²= ½ x 20 x (2) ² = 40 J

.·. Loss in kinetic energy = E1 – E2 = 250 – 40 = 210 J

Work done by the force W = Change in kinetic energy = -210 J

The negative sign of work shows that there is decrease in kinetic energy of the mass.

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