A 6000 kg train car traveling at 2.5 m/s collides with another 6000 kg train car, now they are both moving but with a speed of 1.25 m/s. This is an example of Conservation of Momentum.You can prove it by (6000kg)(2.5m/s)+(6000kg)(0m/s= (6000+6000kg)(1.25m/s).
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