Physics
posted by Anonymous .
A railroad car with a mass of 12400 kg collides and couples with a second car of mass 18700 kg that is initially at rest. The first car is moving with a speed of 7.7 m/s prior to the collision.
(a) What is the initial momentum of the first car?
(b) If external forces can be ignored, what is the final velocity of the two railroad cars after they couple?

Physics 
Henry
a. Momentum=m1*V1 = 12,400 * 7.7=95,480
b. Momentum = (m1+m2)*V = 95,480
m1 = 12,400 kg
m2 = 18,700 kg
Solve for V.
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