Your Name ______Pd _____

Lab Partners ______

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Hooke’s Law Lab

Purpose: In this lab you will be verifying the relationship between the force (in this case a weight or “Fg”)

applied to a spring and the amount of deformity (stretch or “x”) that results. This deformation

behavior is know as Hooke’s Law.

You’ll do this by graphing force versus deformation and determining what the relationship is by

calculations and by assessment of the slope of your graph.

Procedure: 1. Zero your mirror scale so that the flat base of the hanger matches up with the zero mark on the

scale. Make sure that the mirror image of the scale base is completely hidden by the actual base

2. Beginning with 0 grams, record the level of the hanger base. The level of the base represents

the total stretch (“x”) of the spring. Continue adding mass in increments of 100 grams,

recording the total mass in grams on your data chart each time and the new level of the

hanger base to the nearest tenth of a centimeter each time up to 600 grams total mass.

3. Convert the masses in grams to masses in kilograms and record on your data chart.

4. Convert the masses in kilograms to weights in newtons and record on your data chart.

5. Convert the stretch in centimeters to stretch in meters and record on your data chart.

6. Calculate and record the values of the spring constant “k” for each force/stretch pair using the

Hooke’s Law equation:

F = kx

7. Find the average of the spring constant values and record this value on your data chart.

8. Plot a graph of the force (y-axis) versus the total stretch (x-axis).

9. Find the slope of the graph. Do not use points on your data table to obtain the slope..

Use your Line Of Best Fit!.

Pick two points on your graph’s line of best fit and find the slope from the graph line.

10. Use a percent error calculation to compare the value for the spring constant you found

from the slope of your graph to the average value you found by calculation. Consider that the

calculated value is the truer of the two values.

Data Table:

Trial / Mass (g) / Mass (kg) / Weight (N) / Original Spring
Height (cm) / Stretched spring Height (cm) / Total Stretch (cm) / Total Stretch
(m) / Spring Constant (N/m) / Slope of Force vs. Stretch Graph / % Error Slope versus Calculated K
1
2 /
3
4
5
6
7

Questions: Answer these questions in complete sentences, explaining your answer where appropriate.

1.  Write the equation for your graph in terms of y, m (slope), and x.

2.  Write the equation for your graph in terms of F, k, and x.

3.  What mass would be needed to cause a stretch of 75 cm? (show calculations)

Sample Calculations:

Quantity Calculated / Formula Used / Substitution / Answer with Units
g to kg
mass to weight “Fg”
cm to m
spring constant “k”
average “k”
slope of graph “k”
% error of “k”s