# Homework Help: Momentum Vs. Energy?

1. Feb 23, 2004

### derfrok

okay, in class my teacher explained to us a problem where he threw up two lumps of clay into the air where the 2nd one was suspended in mid-air and the 1st one was thrown up into it. They collided and stuck to each other. He wanted us to figure out the distance the two parts of clay traveled.

Okay, the question is really this.. How come it's a Energy Problem rather than a Momentum problem? TIA

2. Feb 23, 2004

### Koveras00

can you post the whole question up? this description is abit brief...

3. Feb 23, 2004

### HallsofIvy

The problem makes not a whole lot of sense! Two lumps of clay were thrown in the air? Then how was one "suspended" in mid-air? Were they thrown directly up or at an angle? Exactly what distance are you talking about?

4. Feb 24, 2004

### Chi Meson

I recognize this question because it seems to be in every textbook.
(One ball of clay is help by a thread or something)

It does require analysis of both energy and momentum:

in short, you use the conservation of momentum to analyze all problems that feature collisions. Immediately after the collision (the first infinitesimal moment of time)it becomes a conservation of energy problem where the kinetic energy transforms into potential energy.

5. Feb 24, 2004

### derfrok

yup that's it.. can you ellaborate more on why after the collision the KE becomes PE in this case? TIA