Question

FIGURE 6 shows a 3.0 kg box sliding down with constant speed u = 1.2 ms-1 along a rough plank inclined at an angle 25o with the horizontal. Calculate the rate of work done by the frictional force on the block. (Given g = 9.81 ms-2)

Answer 1

$A_{fr}=-\frac{mv^2}2+mgl\sin\alpha=-860~J.$