# Homework Help: Masses placed on platforms, with compressed spring under them.

1. Sep 24, 2011

### springwave

1. The problem statement, all variables and given/known data

Two balls of masses m1& m2 are placed on different platforms, which are subjected to springs of same force constant and same compression. (springs are under platforms, basically like launch pads to fire the balls into the air). When the platform of first ball is released, m1 rises to maximum height in 4 seconds. Find the time in which the other ball will rise to it's maximum height

T1 = 4 s
2. Relevant equations

Spring PE = 1/2 kx2

3. The attempt at a solution

I tried solving the problem neglecting the time taken for the spring restore it's length,(only considering time of flight, after ball loses contact with platform)
But the answer doesn't seem to match.

I'm unable to calculate time taken for spring to restore it's length.
I hope someone can give me some direction on how to proceed.

2. Sep 24, 2011

### danielakkerma

Hey...
Do you mean that the ball/whatever leaves the platfrom immediately upon release?
Please clarify, before we can proceed, how each of the masses behaves after the springs are free to operate.
Thanks,
Daniel

3. Sep 24, 2011

### springwave

The balls are initially at rest on the platforms when they are compressed.
They loose contact only after the spring has restored it's length