A force given by the relation F = 8t, (F in Newton and t in sec.) acts on a body of mass 2kg. Initially at rest. Choose the correct option.

Options

A. Power of force is continuous increasing.
B. The work done by this force on the body during first 2 seconds of its motion is 64 J.
C. Velocity at 2 seconds after beginning of motion is 8 m/s.
D. Power of force is constant.

Answer

A, B, C

Explanation

Let the both blocks are moving together, then `a = (60)/(40) = 1.5 m//s^(2)`
thus, force on lower block has to be F = Ma = `30 xx 1.5 = 45N`
Next `f_(L) = mu N = 0.5 xx 10 xx 10 = 50 N`
Since `F lt f_(L)` , both the blocks will move together, thus force of friction = 45N