physics
posted by joey .
A bullet of mass 8 g strikes a ballistic pendulum of mass 2.0 kg. The center of mass of the pendulum rises a vertical distance of 10 cm. Assuming that the bullet remains embedded in the pendulum, calculate the bullet's initial speed.

The momentum of the bullet: massbullet*velocity
that has to equal the momentum of the block and bullet combination at impact(mblock+massbullet)V set them equal, and solve for V.
Now, the initialKE of the block and bullet combination is 1/2 (totalmass)V^2
set that equal to the change in PEnergy
totalmass*g*height.
solve for height in terms of initial bullet velocity.
WEll, you know height, so you can solve for bullet velocity. 
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