Hooke’s Law

Objective: Determine the elastic constant of various springs

Materials: Hooke’s Law Apparatus, springs, masses

Procedure:

  1. Set up the Hooke’s Law Apparatus using the larger spring as shown in the kit’s instructions.
  2. Adjust the mirrored scale until the pointer is initially set at or near the zero mark. Record this initial position in Data Table I.
  3. Place a 100g mass on the hanger. Multiply by 9.8 m/s/s to obtain the weight in Newtons.
  4. Record the final position of the pointer in Data Table I.
  5. Determine the change in position of the pointer.
  6. Divide the amount of force (weight) put on the spring by its change in position to obtain the spring’s elastic constant.
  7. Repeat this procedure until Data Table I is complete.
  8. Determine the average value of the elastic constant for all 10 trials.
  9. Carefully replace this spring with the smaller spring.
  10. Repeat these procedures until Data Table II is complete.

Data Table I

mass,
kg / weight,
N / initial position,
cm / final position,
cm / ∆ position,
cm / elastic constant,
N/cm
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
Average elastic constant =

Data Table II

mass,
kg / weight,
N / initial position,
cm / final position,
cm / ∆ position,
cm / elastic constant,
N/cm
0.040
0.080
0.120
0.160
0.200
0.240
Average elastic constant =

Results:

  1. Make a graph of “Force on Spring vs Elongation” for each spring.
  2. Find the best-fit linear equation of your curve and record on your graph.

Conclusion:

  1. Compare each spring’s average elastic constant with the slope of its graph.
  1. Write an equation for each spring that will allow one to calculate how far it will stretch when the force on it is specified.
  1. Name sources of error for this activity.

Extension:

Determine the elastic constant of the springs in the 0-20 N and 0-10 N force scales. Describe your method below.

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