A 6.0-kg block slides along a horizontal surface. If µk = 0.20 for the block and surface, at what rate is the

Question

A 6.0-kg block slides along a horizontal surface. If µk = 0.20 for the block and surface, at what rate is the friction force doing work on the block at an instant when its speed is 4.0 m/s?

-59 W

-47 W

-71 W

-82 W

+71 W

Answer 1

rate of the friction force (P) doing work on the block must be negative cause always resists the motion.

P=F*V so

P= µk*m*g*v

P=0.20*6*9.81*4

P=--47 W