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A 480kg car moving at 14.4m/s hits from behind another car moving at 13.3m/s in the same direction. If the second car has a mass of 570kg and a new speed of 17.9m/s what is the velocity of the first car after collision?

Since there is a velocity for one car after the collision and the question asks for the other car's velocity after the collison this collision must be elastic.

Thus

m1v1 + m2v2 = m1v1f + m2v2f

480*14.4 + 570*13.3 = 480v1f + 570*17.9

14493N = 480v1f + 10203N

4290N = 480v1f

8.94m/s = v1f

Is this right?