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