A crate of mass 10.0 kg is pulled up a rough incline with an initial speed of 1.
ID: 1978198 • Letter: A
Question
A crate of mass 10.0 kg is pulled up a rough incline with an initial speed of 1.50 m/s. The pulling force is 100 N parallel to the incline, which makes an angle of 18.0° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 5.55 m.
(a) How much work is done by gravity?
Correct: Your answer is correct. -168.074J
(b) How much mechanical energy is lost due to friction?
Correct: Your answer is correct. 206.912J
(c) How much work is done by the 100 N force?
Correct: Your answer is correct. 555J
(d) What is the change in kinetic energy of the crate?
Your response differs from the correct answer by more than 100%. J
(e) What is the speed of the crate after being pulled 5.55 m?
m/s
Explanation / Answer
Given that Mass of the crate m = 10 kg Initial speed of the crate vi = 1.5 m/s ---------------------------------------------------------------------------------------- (a) How much work is done by gravity?Correct: Your answer is correct. -168.074J
(b) How much mechanical energy is lost due to friction?
Correct: Your answer is correct. 206.912J
(c) How much work is done by the 100 N force?
Correct: Your answer is correct. 555J
----------------------------------------------------------------------------------------- (d) From work energ theorem the change in kinetic energy = net work done KE = 555 J - 168.074 J - 206.912 J = 180 J (e) The initial kinetic energy Ki = 1/2 mvi2 = (0.5)(10 kg) (1.5 m/s)2 (e) The initial kinetic energy Ki = 1/2 mvi2 = (0.5)(10 kg) (1.5 m/s)2 = 11.25 J From work energy theorem Kf - Ki = W 1/2mvf2 - 11.25 J = 180 J 1/2mvf2 = 191.25 J vf2 = 2 (191.25 J)/10 kg = 38.25 Therefore the final velocity vf = 6.18 m/s
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