W fric = -421.4 J Correct W net = _________ J An Eskimo returning from a success

Question

Wfric = -421.4 J Correct Wnet = _________J An Eskimo returning from a successful fishing trip pulls a sled loaded with salmon. The total mass of the sled and salmon is 50.0 kg, and the Eskimo exerts a force on the sled by pulling on the rope. Suppose the coefficient of kinetic friction between the loaded sled and snow is 0.200. (a) The Eskimo pulls the sled 4.30 m, exerting a force of 1.30 10^2 N at an angle of ? = 0?. Find the work done on the sled by friction, and the net work. Wfric = -421.4 J Correct Wnet = _________J (b) Repeat the calculation if the applied force is exerted at an angle of ? = 30.0? with the horizontal. Wfric = J Wnet = J

Explanation / Answer

a) work done against friction Wf = u m g S = 0.2 x50 x9.8 x5.4 = 529.2 J ner wrk done Wnet = F S - Wf = 105 x5.4 - 529.2 = 567 - 529.2 = 37.8 J b) now also Wf = u m g S = 529.2 J but net work done Wnet = FS cos(30) - Wf = 105 x 5.4 x0.866 - 529.2 = - 38.2 J(negative work)

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