Hi, and first of all, I'd like to thank you for reading this. I also posted this to HomeworkHelp in the hopes of getting an answer sooner, so I'm going to copy and paste what I typed there.

I performed an experiment in class the other day involving springs and now I have to determine the spring constant of the spring. We used 2 methods to do so.

1: We had a spring hanging vertically off a stand, with a weight hanger attached onto it. We put a ruler behind it and kept the ruler in place with the stand, and determined the initial position of the spring on the ruler (0 cm). Then we started adding weighted discs onto the weight hanger on the spring and measuring the amount of stretching that the spring did by reading the ruler. We did this for a couple different weights.

2: We just put a 50g mass on this same spring and pulled it, then released it so that it would start oscillating. Then we used a stopwatch to record the time that it took for 1 period.

So with method 1, I was planning to do a force vs displacement graph, the slope of which would be the spring constant, since F = kx, so k = F/x. The restoring force is equal in magnitude to the force of gravity, which is equal to mg, and x is determined by the ruler measurements. But my question is - does the mass of the weight hanger itself matter? It was attached to the bottom of the spring, and we put the extra weighted discs on top of this weight hanger. Our setup looked like this: http://www.4physics.com/phy_demo/HookesLaw/HookesLawLab.html While performing the experiment, I assumed it didn't matter, so I didn't think to use a balance to find its mass. My reasoning was that we measured the initial position of the spring (0 cm) with the weight hanger already on it, so any change in displacement would only be caused by the extra weights we added, right? At least that's what I thought, but after graphing the force vs displacement and applying a linear fit, I got a positive y intercept. Is this the weight of the weight hanger? Or is the y intercept not 0 merely because of uncertainties when I read the ruler? I didn't even record the mass of the weight hanger so I'm kind of worried. I thought my reasoning made sense but now I'm not so sure.

As for method 2, I was just planning on using the equation T = 2π√(m/k), but once again, if m is the mass of the weight hanger the extra weight I put on, then the calculations will be thrown off.

Can anyone please confirm that what I'm doing (force vs displacement graph for method 1, equation for method 2) is correct, and also tell me whether or not the mass of the weight hanger matters in this situation? If so, is it the y-intercept on my graph? Thanks a ton.