Homework Help: Spring constants

1. Aug 18, 2009

dance_sg

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

A 7.50-kg ball is placed on top of a spring with a spring constant of 475 N/m that has an initial length of 35.0 cm (h1). When the ball has reached its equilibrium position, it is supported by both springs at a height of 20.0 cm above the table (h3). If the shorter spring has an initial length of 25.0 cm, what is its spring constant?

2. Relevant equations

f=-kx

3. The attempt at a solution
would i find the force for h1 then use that number and 25.0 cm (0.25m) to find the spring constant? or do i have to find the force of h1 and h2, add them up, then divide that nu,ber by0.25m to find k..

2. Aug 18, 2009

kuruman

Is there a picture that goes with this? The description you gave is inadequate to help me figure out what is going on.

3. Aug 18, 2009

dance_sg

yes there is, i dont know how to upload the image tho. when i try it says invalid file type

4. Aug 18, 2009

kuruman

Is your file one of "bmp doc gif jpe jpeg jpg m ms mw mws nb pdf png psd txt xls zip"? Is it perhaps too big?

5. Aug 18, 2009

dance_sg

ya i think its too big

6. Aug 18, 2009

dance_sg

im trying to make it work right now. i think it may!

7. Aug 18, 2009

dance_sg

Attached Files:

• diagram.jpg
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8. Aug 19, 2009

kuruman

OK, I think I understand now. One spring supports the 7.50-kg ball when it is compressed by 0.15 m. The other spring supports the 7.50-kg ball when it is compressed by 0.05 m.

Draw a free body diagram, put in all the forces and find an expression for the distance by which the spring is compressed in terms of the ball's weight and the spring constant.