Help please! 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?