Science Buddies: "Ask an Expert"

I built a model of the knee to measure the stress put on the patella. To do so, I must use hooke's law. I under stand that in f=-kx, x is the distance, but how do I find the k variable? The k variable being the spring constant of the spring...how do I find it? Please please please help! My project is due on Jan 24th!

Hi vancan007,

To calculate the spring constant, k, you will need to measure the force you apply to the spring to stretch the spring by a certain distance. Then, plug the force and distance into Hooke's law and solve for k. For example, let's say that I applied 10 Newtons of force to the spring, and the spring extended by 20 cm. Since

f = -kx
-f/x = k
-10 newtons/0.2m = k
k = -50 Newtons/meter

Thank you so much!