A body of mass 2 kg starts from rest and moves in a uniform acceleration. It acquires a velocity of `20 ms^(-1)` in 4 s. The power exerted on the body at 2 s in watt is 

Options

A. 50
B. 100
C. 150
D. 200

Answer

B

Explanation

Here, `u = 0 , m = 2 kg`
Let a be the uniform accelration.
Using , `v = u + at`
`:. 20 = 0 + a(4) or a = (20)/4 = 5 ms^(-2)`
Force , `F = ma = (2 kg)(5 ms^(-2)) = 10 N`
The velocity acquired by the body in 2s is
`v = at = (5 ms^(-2))(2s) = 10 ms^(-1)`
Power exerted on the body is
`P = Fv = (10 N)(10 ms^(-1)) = 100 W`.