A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air friction, how fast will it be going when it gets to the bottom?
(A) 12m/s. (B) 28m/s. (C) 40m/s. (D)1600m/s
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(A) 12m/s. --- No.
P.E. = mgh. Don't forget g=10m/s
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(B) 28m/s. --- No.
K.E. = (1/2)mv. Don't forget the 1/2.
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(C) 40m/s --- Yes.
(1/2)mv = mgh:
v = 2gh = (2)(10)(80)m/s = 1600m/s
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(D) 1600m/s --- No.
K.E. = (1/2)mv.
Don't forget that v is squared.
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