A block of mass 1 kg is placed at the point A of a rough track shown in figure. If slightly pushed towards right…..

Q: A block of mass 1 kg is placed at the point A of a rough track shown in figure. If slightly pushed towards right, it stops at the point B of the track. Calculate the work done by the frictional force on the block during its transit from A to B. (g = 10 m/s²)

(a) -2 J

(b) -2 .5 J

(c) -4 J

(d) -3 J

Ans:(a)

Sol: Loss in P.E = Work done against friction

$ \displaystyle mg(h_1 – h_2) = W_f $

$ \displaystyle 1 \times 10(1 – 0.8) = W_f $

W_f = 2 J

Work done by the frictional force = – W_f = – 2 J