Spring distance vs force lab question

[proace360]

Homework Statement

In our lab, we had springs of different tolerances hung off of a holder (I can't really describe it) by one end and dangled different masses on the other end. We had to put the data that we collected of displacement and force on a graph and find the linear best fit line.

On one of the analysis questions, it asked what the value of the y-intercept described and why, and our values were between .5 and 1.5 for the different strings. With a y-int, that means that when the distance is zero there is a force acting on the spring. We assumed that it was the weight force, but the teacher said that it wasn't and it was some other "thing". I don't know what that thing is and I was wondering you could help me. I understand that the slope is the k value, but what does the y-int mean?

they were like force=27.5(distance)+.819 or something like that

Homework Equations

f=kx

The Attempt at a Solution

In the wall of text

 

[proace360]

Still no one can help me :(?

 

[Doc Al]

If no force stretched the spring, what would the distance measurement mean?

 

[proace360]

Well, the distance is on the x-axis and the force is on the y, so the question is what having no distance but still having a force means

 

[Doc Al]

Well, the distance is on the x-axis and the force is on the y, so the question is what having no distance but still having a force means

Right. I asked you the opposite question: When the force is zero, what does the distance measurement mean?

 

[proace360]

Oh, well if the force is zero, than the distance measurement is the displacement the spring experiences with no force acting on it.

 

[Doc Al]

Oh, well if the force is zero, than the distance measurement is the displacement the spring experiences with no force acting on it.

Well, yeah... But what does that mean?

When you measured "distance", what did you actually measure? The displacement measured from what point?

 

[Doc Al]

If you're still drawing a blank on my question, here's another version: If you remove the applied force on the spring, why isn't the displacement zero?

 

[proace360]

Well, I thought it was due to the the weight of the spring, but my teacher said that that was wrong. I have no clue why it wouldn't be zero any other way.

 

[Doc Al]

Did you take into consideration the unstretched length of the spring?

 

[proace360]

well, we took the initial measurement of the string from while it was hanging to eliminate weight as a force acting on the spring (since it would be constant). I'm confused by what you mean with unstretched length because we weren't required to take that measurement.

 

[Doc Al]

well, we took the initial measurement of the string from while it was hanging to eliminate weight as a force acting on the spring (since it would be constant). I'm confused by what you mean with unstretched length because we weren't required to take that measurement.

When you say you measured displacement, what did you actually measure? Displacement from what? If you hung the spring without any weights on it, does that count as zero displacement? When you hung a weight, did you measure the additional displacement from the position it had when no weight was hung?

Since I don't have the details of what you actually did, I can only guess. (A diagram would help if you had one.)

 

[proace360]

I'll see if I can make one

EDIT: Here we go. What we did was measure the initial length of th spring like this, then added a weight, measured the length of the spring, and subtracted initial from the new length for the dsiplacement.

 

[proace360]

When you say you measured displacement, what did you actually measure? Displacement from what? If you hung the spring without any weights on it, does that count as zero displacement? When you hung a weight, did you measure the additional displacement from the position it had when no weight was hung?

Since I don't have the details of what you actually did, I can only guess. (A diagram would help if you had one.)

Yes, with no additional weight to the spring would be zero displacement. When more weight was hung, we measured the length of the spring and subtracted the original additional-weightless length for the displacement.