college physics
posted by barbara .
a railway freightbcar whose mass is 15 000kg & speed is 2.4m/s runs into a stationary freight car whose mass is 25 000kg. the 2 cars couple & roll off the track. what is the speed if the 2 cars as tey move together down the track? and how much kinetic energy is lost in the collision?

a. use conservation of momentum.
(m+M)V=m*2.4+M*0 solve for V.
Next,
lost KE= initial KEfinal KE=1/2 m*2.4^21/2 (m+M)V^2