# General Rule for Spring Compression?

1. Dec 7, 2008

### FrenchAtticus

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

A block of mass m slides on a horizontal frictionless table with an initial speed. It then compresses a spring of force constant k and is brought to rest. How much is the spring compressed x from it's natural length.

2. Relevant equations

??

2. Dec 7, 2008

### mgb_phys

Conservation of energy.
Whats the energy of a moving block
Whats the energy of a compressed spring

3. Dec 7, 2008

### FrenchAtticus

Conservation of energy is mgh1 + 1/2mv1^2 = mgh2 + 1/2mv2^2

energy of a moving block is 1/2mv^2

energy of a compressed spring is potential?

How do I apply these to find how much the spring will compress.

4. Dec 7, 2008

### mgb_phys

No this is only for a falling object mgh2 = gravitational potential energy.

Whats the equation for the energy in a compressed spring?

5. Dec 7, 2008

### FrenchAtticus

energy in a compressed spring is F = -Kx

and is conservation of energy m1v1 = m2v2?

6. Dec 7, 2008

### mgb_phys

No that's momentum.
Spring energy = 1/2 k x^2
Kinetic energy = 1/2 m v ^2

For conservation of energy you have the ke of the block at the start and the spring energy at the end. So the ke just equals the spring energy.