Posted by **ray** on Monday, May 24, 2010 at 10:11am.

4. Two masses of 3 kg and 5 kg collide head-on, the former moving to the right with the speed 5 m/s and the latter moving to the left with the speed 3 m/s.After collision they stick together. What amount of mechanical energy is lost?

5. A cylinder with a uniform density is rolling over a plane. What fraction of its kinetic energy is rotational kinetic energy?

- physics -
**drwls**, Monday, May 24, 2010 at 11:26am
4. Their momenta cancel and the stuck-together mass won't move, because

5x3 - 3x5 = 0.

All mechanical energy is lost.

5. Compare (1/2) I w^2 (the rotational KE) with the sum of (1/2) Iw^2 and (1/2) M V^2.

Note that I = (1/2) M R^2 (for solid cylinders) and

V = R w (for rolling objects). You should end up with a fraction independent of M, R and w.

## Answer This Question

## Related Questions

- physics - A block of mass m1 = 2.4 kg initially moving to the right with a speed...
- Physics -Conservation of Momentum- - 1) A 1 kg mass moving at 1 m/s has a ...
- Physics -Conservation of Momentum- - 1) A 1 kg mass moving at 1 m/s has a ...
- physics - A 5-kg motorbike moving at 10m/s to the left collides with 6-kg ...
- Physics ~really need help!~ - 1) A 1 kg mass moving at 1 m/s has a totally ...
- Physics - Car A is moving at a constant speed of 10.0 m/s and passes Car B ...
- physics - One object is at rest and another is moving. The two collide in a one-...
- Physics - A block of mass m1 = 2.4 kg initially moving to the right with a speed...
- Physics - A block of mass m1 = 2.4 kg initially moving to the right with a speed...
- physics - A hockey puck moving due east with speed 1.00 m/s collides with an ...

More Related Questions