# Homework Help: Pellet colliding with hanging mass example. Having trouble finding height.

1. Dec 10, 2012

### folsomfighter

A 1-kg pellet travels with velocity 280 m/s to the right when it collides with a 39-kg hanging mass which is initially at rest. After the collision, the pellet remains lodged in the hanging mass, i.e., it is a completely inelastic collision. The hanging mass (+pellet) then swings upward and reaches a maximum height hmax before swinging downward again. Assume that no external forces are present and therefore the momentum of the system is conserved. Solve for final velocity, final kinetic energy, and maximum height in centimeters.

Thus far, I've figured out the final velocity using the formula p(initial)=p(final), where p=mv. I've also solved for the final velocity using k(final)=.5*m*v^2.

v(final)=7 m/s
k(final)=980j

But I'm stumped on what equation to use to solve for the max height.

2. Dec 10, 2012

### SammyS

Staff Emeritus
Hello folsomfighter. Welcome to PF !

If the collision occurs at time, t=0, then for any time, t>0, conservation of (mechanical) energy is in effect.