# Conservation of momentum and energy

1. Mar 14, 2005

### krypto

Conservation of momentum and energy :D

Wats this question on bout?

1. [HRW6 10.P.026.] In Fig. 10-32a, a 4.00 g bullet is fired horizontally at two blocks at rest on a frictionless tabletop. The bullet passes through the first block, with mass 1.20 kg, and embeds itself in the second, with mass 1.80 kg. Speeds of 0.630 m/s and 1.40 m/s, respectively, are thereby given to the blocks (Fig. 10-32b). Neglect the mass removed from the first block by the bullet.
(a) Find the speed of the bullet immediately after it emerges from the first block.
(b) Find the bullet's original speed.

2. Mar 14, 2005

### Galileo

As it says, use conservation of momentum and energy.

Calculate the initial momentum and energy.
Calculate the momentum and energy after the bullet passes the first block.
Calculate the final momentum and energy after the bullet is embedded in the second block.

The momentum and energy don't change throughout the process.

3. Mar 14, 2005

### krypto

Thnx for that help, it was really confusin me!