Railcar weighs 4.5 tons and travels to the right at 7m/s. It collides with railcar B initially at rest and weighing 3.75 tons. If two car link together, what is their velocity after the collision?

We first need to convert tons to kg, 1 ton = 907kg, so 4.5 * 907 = 4081.5 kg = Mass

Velocity = 7 m/s

So, 4081.5 * 7 = 28570.5 kg*(m/s) = momentum

By law of conservation of momentum, the momentum of moving object after collision should be the same, which is why we simply add the mass of railcar B to the mass of railcar A, and apply the same equation

We first need to convert tons to kg for railcar B: 3.75 * 907 = 3401.3 kg