Why do different masses give slightly different K values for the same spring?

[Crusaderking1]

Confused on receiving just one K value for elongation and oscillation

Homework Statement

Ok. For lab, I had to place 5 different masses on a spring and calculate its initial and final position. I did this with a small, medium and large spring.

Then after I gathered my values, I made a graph, and fit a trendline through it.

The book says to use the slope and Hooke's law to find the K constant. However, when I use the slope and equation, I get very slightly different K constant values for the different masses on the same string. (like 4.311 for 0.05kg, and 4.317 for 0.06 kg).

How am I suppose to get just one K constant using the slope and equation? The book probably would have told me to average the K values if I was meant to get more than one.


Same scenario applies for the oscillation of the spring.

What should I do? Thanks.

Homework Equations

The Attempt at a Solution

 

[Spinnor]

The spring constant probably did not change. It was an experiment! There is going to be error (your numbers were still pretty close).

 

[Crusaderking1]

The spring constant probably did not change. It was an experiment! There is going to be error (your numbers were still pretty close).

Yes, I see your point.

I am suppose to use the slope to find one k value. I suppose that the trendline is suppose to provide values of the line that all equal the "average k", which I think I need.

However, I do not know how to choose a point on the trendline using excel(not a point used to find the trendline).

I think that's what I need, since I can plug that y-value and x-value into the equation F=k(y-yo), which will give me the one k value I need. I just don't know how to select a point on the trendline.