Question

You are pushing a 150-kg wooden crate in a straight line a distance of 4.5 m across a wooden floor. The crate is speeding up at 0.48 m/s2. The static and kinetic coefficients of friction are 0.42 and 0.30, respectively. What is the work done by YOU on the crate?

Answer 1

Since the crate is moving use the kinetic coefficient of friction. Ff = 150 * 9.8 * 0.30 = 441 N Work done by friction force = 441 * 4.5 = 1984.5 N * m
Since the crate is accelerating, the force with which you push the crate must be greater than the friction force. Net force = F – 441 = 150 * 0.33 F = 441 + 49.5 = 490.5 N This is the force which you exerted