Question

A railway truck travelling along a level track at 5.0 m s−1

collides with a truck of twice the
mass moving in the same direction at 2.5 m s−1
. The trucks couple together and continue
moving. Calculate
(i) the final speed of the combined trucks, and
(ii) the percentage of the kinetic energy lost in the collision.

Answer 1

(i) conserve momentum

m*5 + 2m*2.5 = (m+2m)v
(ii) before: 1/2 (m*5^2 + 2m*2.5^2)
after: 1/2 (m+2m)v^2
lost = before-after
%lost = lost/before