Sand is being dropped on a conveyor belt at the rate of M kg/s. The force necessary to keep the belt moving with a constant velocity of v m/s will be:

Options

(a) Mv newton
(b) 2 Mv newton
(c) Mv/2 newton
(d) zero

Correct Answer:

Mv newton

Explanation:

F = d(Mv) / dt = M . dv / dt + v . dM / dt
v is constant,
F = vdM / dt But dM / dt = Mkg / s
F = vM newton.