# Two masses on a spring...

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1. Apr 5, 2016

### Sho Kano

1. The problem statement, all variables and given/known data
Two masses A, and B both sit on a vertical spring. If the spring is compressed then released, why do A and B rise to the same height? (the mass of A is greater than that of B)

2. Relevant equations
P = mgh
S = 1/2kx2
K = 1/2mv2

3. The attempt at a solution
Both masses rise to the same height, I treated the two blocks as a system, because the spring propels them both in the air. Why is this? How much energy does each block have?

2. Apr 5, 2016

### haruspex

Would you expect them to be travelling at the same speed when contact with the spring is lost?

3. Apr 5, 2016

### Sho Kano

Intuitively yes?

4. Apr 5, 2016

### haruspex

Ok, so using the SUVAT equations, what determines the height to which a projectile rises?

5. Apr 6, 2016

### Sho Kano

Initial velocity

6. Apr 6, 2016

### haruspex

Putting that together with your answer in post #3, does that answer your question?

7. Apr 6, 2016

### Sho Kano

Yes! But from an energy point of view, mass A has more energy right?

8. Apr 6, 2016

Yes.