# Homework Help: Find the maximum spring compression

1. Oct 4, 2011

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

A horizontal spring with k = 71 N/m has one end attached to a wall and the other end free. An 95 g wad of putty is thrown horizontally at 3.7 m/s directly toward the free end.

Find the maximum spring compression.

2. Relevant equations

W=1/2kx^2

3. The attempt at a solution

Tried squaring the 3.7m/s to get 13.69m^2/s^2 and multiplying that by the weight of the putty to obtain 1.3J, the work done.

Plugging that in...

W=1/2kx^2
1.3J=1/2(71)x^2
x=0.19

which is incorrect.

2. Oct 4, 2011

### cepheid

Staff Emeritus
Multiplying it by the mass of the putty, not the weight.

In any case, I suspect you are missing the factor of 1/2 in the expression for the kinetic energy.

3. Oct 4, 2011

I doubled the KE when I multiplied the 1/2 over in the second step, is that what youre talking about?

4. Oct 4, 2011

### cepheid

Staff Emeritus
I'm saying the KE is not 1.3 J, it's half of that. You computed 1.3 J using mv2 when you should have used (1/2)mv2.

5. Oct 4, 2011

Got the right answer after rounding it properly haha. Thank you, that's all for tonight. :)

6. Dec 15, 2011