Car 1 has a of mass 1000kg and is going at 20m/s. Car 2 has the same mass as Car 1 and is stationary. If they collide and travel together as one unit in the same direction as Car 1 was going, calculate the speed of the unit after the collision.

By Conservation of Momentum

Total Momentum Before= Total Momentum After

thus

m1v1+m2v2=(m1+m2)v3

Plugging in the numbers and re-arranging for v3 gives

100020+10000=2000*v3

v3=(1000*20)/2000=10m/s

AH

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