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A body of mass 4kg is acted on by a constant force of 12N fo...

A body of mass 4kg is acted on by a constant force of 12N for 3 seconds. The kinetic energy gained by the body at the end of the time is

A.

144J

B.

162J

C.

81J

D.

72J

Correct answer is B

K.E = 1/2MV2
Force, F = ma => a = F/m = 12/4 = 3ms-2
But a = (V-U) / t => V = u + at
If the initial velocity U = 0, then V = at = 3 x 3 = 9ms-2
∴ K.E, = 1/2ms-2
1/2 4 x 9 x 9 = 162J