In the Figure, a 900-Kg Crate Is on a Rough

Multiple Choice

In the figure, a 900-kg crate is on a rough surface inclined at 30°. A constant external force P = 7200 N is applied horizontally to the crate. While this force pushes the crate a distance of 3.0 m up the incline, its velocity changes from 1.2 m/s to 2.3 m/s. How much work does friction do during this process?

A) -3700 J
B) -7200 J
C) +3700 J
D) +7200 J
E) zero