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: Option B
Explanation
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-21/2 4 x 9 x 9 = 162J