Justin moves a desk 1.90 m across a level floor by pushing on if with a constant
ID: 1520455 • Letter: J
Question
Justin moves a desk 1.90 m across a level floor by pushing on if with a constant horizontal force of 380 N. (It slides for a negligible small distance before coming to a stop when the force is removed.) Then, changing his mind. he moves it back to its starting point, again by pushing with a constant force of 380 V (a) What is the change in the desks gravitational potential energy during the round trip? kJ How much work has Justin done on the desk? kJ If the work done by Justin is not equal to the change in gravitational potential energy of the desk, then where has the energy gone?Explanation / Answer
S = 1.90 m
F = 380 N
a) There is no change in gravitational potential energy of the desk because the movement of the desk is always horizontal.
b) Work Done = 380 x 1.9 + 380 x 1.9 = 1444 J
c) Energy has been dissipated in the form of heat by friction.
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