A 2kg rock is dropped from rest at a height of 30 meters above the ground. How much heat energy is generated when it hits the ground?
(A) 0. (B) 60J (C) 900J (D) 600J
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What this question is about
(A) 0. --- No.
The lost mechanical energy turns into heat.
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(B) 60J --- No.
P.E. = mgh. Don't forget g = 10 m/s
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(C) 900J --- No.
P.E. = mgh.
Nothing is squared in that formula.
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(D) 600J Yes.
Energy = P.E. = mgh
= (2kg)(10 m/s)(30m) = 600J.
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