1Physics
Name___________________________Period____
Conservation of Energy and Calculating µ
Purpose: The principle of conservation of energy will be used to calculate the coefficient of friction.
Materials: Elastic, slotted weights with felt, spring scale, meterstick
Procedure: Part 1
1. Hook the spring scale onto the middle of the elastic and apply a spring force of 1 N horizontally. Record FS.
2. Measure and record the deformation x in meters.
3. Repeat in 1 N intervals as far as the lab desk will allow (2 N, 3 N, etc).
5. Open Vernier Graphical Analysis and graph spring force (y) versus deformation (x).
6. Click the f(x) button on the toolbar and select “linear fit” and “try fit.”
7. Record the slope as the spring constant k of the elastic.
Procedure: Part 2
1. Measure and record the mass of the slotted weight.
2. Load the mass onto the elastic and pull it back some distance xA. Measure and record xA.
3. Release the mass such that it slides across the desktop.
4. Measure and record the distance the mass travels from the relaxed location of the elastic (d).
5. Repeat steps 2-4, using a larger initial deformation xA. Perform 5 trials total.
Theory:
Write the energy equation where point A is the mass loaded onto the elastic and point B is when it comes to rest.
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Solve for the coefficient of friction in terms of K, m, xA, g, and d.
µ=
Data/Calculations
trial
F (N)
x (m)
1
2
3
4
5
6
7
8
Material:
trial
k (N/m)
x (m)
EPEA (J)
m (kg)
WFF (J)
d (m)
µ
1
2
3
4
5
AVG
Material:
trial
k (N/m)
x (m)
EPEA (J)
m (kg)
WFF (J)
d (m)
µ
1
2
3
4
5
AVG
Conclusions:
1. Compare the coefficients of friction found in each trial. What is the range for µ? Is there any trend in your
data? What happens to µ as the xA increases?
2. Now look at the results for the two different materials. Is there a difference in the consistency of the results?
Which material produces the “best” results? What evidence do you have for this judgment?
3. Assume that the k constant you calculated for the elastic is less than the actual. What effect would this
have on your calculated value of µ?
4. List sources of error in this experiment and the specific effects they have on the data and your calculated µ .
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