If the coefficient of kinetic friction between the block and the wall is 0.30, find a) the work done by the force on the block. Answer in units of J.

Question

A 1.0 kg block is pushed 3.0 m at a constant velocity up a vertical wall by a constant force applied at an angle of 28.0 ◦ with the horizontal, as shown in the figure. The acceleration of gravity is 9.81 m/s 2 .If the coefficient of kinetic friction between the block and the wall is 0.30, find a) the work done by the force on the block. Answer in units of J.

Answer 1

1) make a free body diagram with mg pointing vertically down, F pointing up toward the wall at 28 degrees, friction pointing vertically down.

2) sum forces =0 in the direction of the wall to find the Normal force = Fcos(28) = N

3) multiply N*.3 to find the friction force f

4) sum forces vertically up to find Fsin28-f-mg=0

5) solve 4) to find F=48N

6) multiply 48*3 to find the work = 144 J