## measuring knee stress with hooke's law

Ask questions about projects relating to: aerodynamics or hydrodynamics, astronomy, chemistry, electricity, electronics, physics, or engineering

Moderators: MelissaB, kgudger, Ray Trent, Moderators

### measuring knee stress with hooke's law

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!
vancan007

Posts: 3
Joined: Mon Jan 13, 2014 9:35 pm
Occupation: student
Project Question: measuring knee stress with a mechanical model
Project Due Date: January 27, 2013
Project Status: I am conducting my experiment

### Re: measuring knee stress with hooke's law

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
All the best,
Terik
Terik Daly
Expert

Posts: 1069
Joined: Sat Nov 08, 2003 11:27 pm
Occupation: Planetary Scientist
Project Question: N/A
Project Due Date: N/A
Project Status: Not applicable

### Re: measuring knee stress with hooke's law

Thank you so much!
vancan007

Posts: 3
Joined: Mon Jan 13, 2014 9:35 pm
Occupation: student
Project Question: measuring knee stress with a mechanical model
Project Due Date: January 27, 2013
Project Status: I am conducting my experiment