# I need a little info please

1. Aug 30, 2006

### bucky1andonly

is there any formulas for a spring, or any way at all to calculate the weight needed to compress a spring, or do you just have to experiment

2. Aug 30, 2006

### quasar987

Mmh the law is "you have to exert a constant force of kx to maintain the spring stretched a distance x from its position of equilibrium", where k is the spring constant. But ultimately, you have to find k experimentally.

3. Aug 30, 2006

### WhyIsItSo

quasar987 is correct; k can only be determined experimetally. Once you have that:

A simple form of Hooke's law
$$F=-kx$$
F = force. k = spring constant. x = displacement from relaxed (not stretched or compressed). Note the right side is negative to denote "equal but opposite".

Also:
$$PE = \frac{1}{2}kx^2$$.

4. Aug 31, 2006

### Staff: Mentor

The negative sign in Hooke's law indicates that the direction of the restoring force is opposite to the displacement from the unstretched position. For example: Displace the end of the spring to the right, the spring force acts to the left.

5. Aug 31, 2006

### Staff: Mentor

...if you don't have K, though, you can still calculate it from the properties of the material and shape of the spring.

6. Aug 31, 2006

### bucky1andonly

thx, that helped a lot

7. Sep 1, 2006

### Hootenanny

Staff Emeritus