Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.

Measuring coefficients of friction

Your job: measure both the static and kinetic coefficients of friction between a whiteboard and an eraser. You must turn in a report which contains

  1. two diagrams, showing your two experiments
  2. two tables, listing all your measurements
  3. neat, legible calculations, showing step-by-step how to go from the measurements to the coefficients of friction
  4. the static and kinetic coefficients of friction, each with an uncertainty
  5. the kinetic coefficient is usually smaller than the static coefficient; does your data follow this rule?
  6. a comparison of your results with those of at least two other groups; do the values agree within the uncertainties?

Static friction

Place an eraser on your whiteboard. Tilt the board until the eraser just starts to slip.

What is the coefficient of static friction between eraser and board? (Hint: make a table showing all forces acting on the eraser).

Kinetic friction

Place the whiteboard flat on the table. Give the eraser some known kinetic energy by sliding it at a measured speed v. Explain how you do this!

Release the eraser and let it skid to a halt; measure the distance L between the release point and its final resting place.

Use the conservation of energy to figure out the size of the friction force between eraser and board; then calculate the coefficient of kinetic friction between eraser and board.

Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.