A 30 ton rail car and a 90 ton rail car, initially at rest, are connected together with a giant but massless compressed springbetween them. When released, the 30 ton car is pushed away at aspeed of 4.0 m/s relative to the 90 ton car. What is the speed ofthe 30 ton car relative to the ground?

Question

Madeline Woods

Physics

2 April, 16:24

A 30 ton rail car and a 90 ton rail car, initially at rest, are connected together with a giant but massless compressed springbetween them. When released, the 30 ton car is pushed away at aspeed of 4.0 m/s relative to the 90 ton car. What is the speed ofthe 30 ton car relative to the ground?

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Answers (1)

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Lloyd · Answer 1

V2 = 1.33m/s

Explanation:

M1 = 30 ton

M2 = 90 ton

V1 = 4 m/s

V2 = ?

Assumption: momentum conserved, no friction

initial momentum = final momentum = 0

momentum : p = MV

(M1*V1) - (M2*V2) = 0

V2 = (30*4) / 90 = 1.33m/s