1. A 870 N crate rests on the floor. (a) How much work is required to move it at
ID: 1421578 • Letter: 1
Question
1. A 870 N crate rests on the floor.
(a) How much work is required to move it at constant speed 6.7 m along the floor against a friction force of 180 N?
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(b) How much work is required to move it at constant speed 6.7 m vertically?
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2. A 310 kg piano slides 4.1 m down a 30° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (Fig. 6-36). The effective coefficient of kinetic friction is 0.40.
(a) Calculate the magnitude of the force exerted by the man.
N
(b) Calculate the work done by the man on the piano.
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(c) Calculate the work done by the friction force.
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(d) What is the work done by the force of gravity?
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(e) What is the net work done on the piano?
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Explanation / Answer
1 a)To move at constant speed, we just need to apply force to overcome the Friction force of 180N
=> Work done = F * s = 180 * 6.7= 1206 Nm
b) To lift verytically at a constant speed, we need to overcome gravity, i.e. nothing but its weight = 985N
Work done = F * s= 870*6.7 = 5829 Nm
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