A 200 g block is released from rest from the top of the rough track shown, from a vertical height of 2 m, and finally comes to rest on the horizontal part. Find the negative of work done by friction in joules.

Question

G1 Physics · Accepted Answer

The block begins and ends at rest, so the net work is zero. Gravity loses potential energy mgh=(0.2)(10)(2)=4 J, which is exactly dissipated by friction. Thus -W(f)riction=4 J.