In the figure below,
the mass is 4.00 kg, and = 30 degrees. The surface does have friction, with s = .45 and k = .39.
If a person takes hold of the rope and, pulling at this angle with a force of T = 29 N, drags the box 3.3 meters...
a. How much work is done on the box by person pulling?
b. How much work is done on the box by the normal force?
c. How much work is done on the box by the force of friction?
d. What is the net work done on the box?
e. If the block starts from rest, what will be its velocity just as the person finishes pulling?
The Attempt at a Solution
a) 29N*3.3m*cos30 = 82.9 J
c) I took 4kg*9.8m/s^2*0.39*3.3m*cos180 = -50.45 which is not correct. What am I doing wrong??