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The force exerted by a spring

If you try to stretch a spring, it will pull back against
you.
The farther you stretch the spring,
the harder it pulls back.
Can you make this simple description more quantitative?

- Acquire one small silver spring. Measure its mass and its
length as it lies horizontally at rest on the table.
- Arrange clamps and bars as shown in the diagram above so that you
can hang the spring from a horizontal bar.
Measure the length of the spring as it hangs by itself;
call this
**L**_{vert}.
- Place 7 various weights, ranging from 0 to 150 grams, on the
bottom of the spring. Measure the length
of the spring for each case.
Compute the distance the spring has stretched
from
**L**_{vert}.
Include uncertainties in this "distance stretched".
- Calculate the force exerted by the spring in each case.
Make a neat table of all your measurements and calculations.
- Make a graph on good graph paper.
The graph should show
**force exerted by the spring**
as a function of **the distance by which the spring
has been stretched**.

- Use your graph to compute the "spring constant" or "force constant"
of your spring. Include uncertainties, and make
sure the units of your values make sense.
- Walk around and talk to at least 3 other groups.
Write down their spring constants (with uncertainties)
and compare them to yours.
Are all the springs in class today "identical"?

####
Optional Extra

At the center table, I will set up a track
tilted at 15 degrees.
We will attach your spring to the track so that it
lies along the track,
and then attach to the lower end
a cart of mass **m** (I'll provide the
actual mass during the class period).
How long will your spring be when it comes
to rest, supporting the car on this tilted track?
Make a prediction.

If your prediction is you gain
within bonus points
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+/- 3 cm +2
+/- 6 cm +1
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