Question

Train cars are coupled together by being bumped into one another. Suppose two loaded train cars are moving toward one another, the first having a mass of 270000 kg and a velocity of 0.275 m/s in the horizontal direction, and the second having a mass of 62500 kg and a velocity of -0.14 m/s in the horizontal direction.what is the final speed?

Answer 1

Conservation of momentum:

m1*v1 + m2*v2 = (m1+m2) v

mass 1 = m1= 270,000 kg

mass 2 = m2= 62,500 kg

initial velocity 1 =v1= 0.275 m/s

Initial velocity 2 = v2= -0.14 m/s

v = final speed

Replacing:

(270,000 * 0.275) + (62,500*-0.14) = (270,000+62,500)v

Solve for v

74,250 - 8,750 = 332,500 v

65,500= 335,500 v

65,500/335,500=v

v= 0.1952 m/s