Posted by **Kayla L** on Monday, October 31, 2011 at 11:29pm.

A 7.0 g bullet is fired horizontally into a 1.5 kg block of wood suspended by a thread. The bullet emerges from the block with a speed of 195 m/s, and the block rises to a maximum height of 12 cm.

Find the initial speed of the bullet.

- PHYSICS HELP!!!!! -
**drwls**, Monday, October 31, 2011 at 11:45pm
First calculate the momentum of the block with the bullet hole in it. Ignore the mass loss of wood, since they provide no information on it.

0.007*Vb = Total Momentum after bullet passes through

= 195*.007 + sqrt(2*g*H)*1.5

Solve for Vb, the initial bullet velocity

H = 0.12 m

sqrt(2*g*H) is the block velocity after the bullet passes through but before it swings upwards.

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