# Inelastic collisions?

1. Aug 9, 2007

### mwahx3

Putty of mass 5 is compresses a spring with stiffness consonant 3. The spring is stretched and the putty has a completely inelastic collision with another putty of mass 15. How fast and how far do the putties travel?

I have no idea how to begin.

thanks,,

2. Aug 9, 2007

### SpitfireAce

me neither...
are you sure it didn't tell you the displacement of the spring, if it gave you that the problem would be solvable

3. Aug 9, 2007

### mwahx3

oh, right sorry. i forgot to include that -- 'with a distance of 6'

thanks for pointing that out.

4. Aug 9, 2007

### SpitfireAce

oh, in that case...
PE=1/2kx^2 for spring.... where k is the stiffness constant and x is the displacement
the spring transfers all its PE to the first putty's KE, so now you want to do KE=1/2mv^2 solving for the velocity of the first putty after it leaves the spring...
then do conservation of momentum.... mv before= mv after
*the mass and velocity before is just the mass and velocity of the first putty, the mass after is the mass of both together and the velocity after is the joint velocity which you are solving for...
uhhh, the distance im not so sure about
you didn't mention any friction in the problem so I assumed there was none... what exactly makes them slow down?