90 N F Example 4.1 30 30 kg A person pulls a 30 kg crate 10 m across a level floor using a rope that is 30 above horizontal. The person exerts a force of 90 N on the rope. (a) How much work is done by the person? (b) If the coefficient of friction between the crate and the floor is 0.1, how much work is done by the friction? (c) What is the work done by the gravitational force? (d) What is the net work done on the crate