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 138000 kg and a velocity of 0.288 m/s, and the second having a mass of 123000 kg and a velocity of -0.131 m/s. (The minus indicates direction of motion.) What is their final velocity

their final velocity is 0.091 m/s

Explanation:

Given;

mass of the first train, m₁ = 138,000 kg

mass of the second train, m₂ = 123,000 kg

initial velocity of the first train, u₁ = 0.288 m/s

initial velocity of the seocnd train, u₂ = -0.131 m/s (opposite direction to the first)

Let their common final velocity after been coupled = v

Apply the principle of conservation of linear momentum;

m₁u₁  +  m₂u₂ = v(m₁  +  m₂)

(138,000 x 0.288)    +    (-0.131 x 123,000)   =   v(138,000 + 123,000)

39,744   -   16,113   =  v(261,000)

23,631 = v(261,000)

v = 23,631 / 261,000

v = 0.091 m/s

Therefore, their final velocity is 0.091 m/s

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