posted by Kayla L .
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.
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.