A train (mass - 1000 kg) starts off at rest at the top of a 16 m hill. It then s

Question

A train (mass - 1000 kg) starts off at rest at the top of a 16 m hill. It then slides down, then up and over a circular hill (radius= 12m) Then it collides and connects to a freight car (mass = 2000 kg) which is initially at rest Friction is negligible (a) How fast is the train going at point A, the crest of the hill? (2) (b) How fast is the train going just before the collision with the freight cat? (2) (c) How fast do the train and car go after the collision (3) (d) Is the kinetic energy of the train+car system conserved, decreased or increased during the collision? Justify your answer. (2)

Explanation / Answer

a. mgh=0.5mv2

v2=2gh=2*9.8*4

v=8.85 m/s

b. v2=2*10*16

v=17.89 m/s

c. 1000*17.89=3000*v

v=5.96 m/s

d. initial k.e =1000*10*16 =160000 j

final k.e =0.5 *3000*5.96*5.96=53333 .333 j

hence kinetic energy has decreased

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