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3. A 75 kg linebacker moving at 6 m/s is running towards an 80 kg tackle moving 4 m/s. If they collide and stick together, how fast will they be moving after the collision?

5. A 6 kg bowling ball and a 4 kg bowling ball are rolled toward each other. The 6 kg ball is initially moving at 5.1 m/s and the 4 kg ball is moving in the opposite direction at 1.3 m/s. If the 6 kg ball slows to 1.5 m/s, what is the final speed of the 4 kg ball?

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3. The sum of the players' momenta is equal to the momentum of the players when they're stuck together:

(75 kg) (6 m/s) + (80 kg) (-4 m/s) = (75 kg + 80 kg) v

where v is the velocity of the combined players. Solve for v :

450 kg•m/s - 320 kg•m/s = (155 kg) v

v = (130 kg•m/s) / (155 kg)

v ≈ 0.84 m/s

4. The total momentum of the bowling balls prior to collision is conserved and is the same after their collision, so that

(6 kg) (5.1 m/s) + (4 kg) (-1.3 m/s) = (6 kg) (1.5 m/s) + (4 kg) v

where v is the new velocity of the 4-kg ball. Solve for v :

30.6 kg•m/s - 5.2 kg•m/s = 9 kg•m/s + (4 kg) v

v = (16.4 kg•m/s) / (4 kg)

v = 4.1 m/s

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