Answer to Question #68279 in Physics for gani

Question

The coefficient of kinetic friction between a 20 kg box and the floor is 0.3.How much work does a pulling force do on the box in pulling it 6 m across the floor at constant speed? The pulling force is directed above the horizontal. (ans: 291.8 J)

Answer 1

The work done is
W=Fs cos⁡α.
Because the box moves at constant speed, the net force is zero. So a pulling force F is equal to friction force F_friction=μmg.
Finally
W=μmgs=0.3×20×9.8×6=352.8 J.