A 60-Kg Block Slides Along a Horizontal Surface

Multiple Choice

A 6.0-kg block slides along a horizontal surface. If µ_k = 0.20 for the block and surface, at what rate is the friction force changing the mechanical energy of the block at an instant when its speed is 4.0 m/s?

A) −59 W
B) −47 W
C) −71 W
D) −82 W
E) +71 W