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Physics Core/AP 1 and 2

LAB: Determining Friction in an Atwood's Machine

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Physics Lab

Physics Lab: Build an Electric Motor

Goal: To observe conversion of electrical to mechanical energy

Materials and Procedure

There is a wonderfully simple lab for building a small working electrical motor, based on a demonstration from Beakman's Science show on TV. Using the instructions at Beakman's Motor to build the motor (weigh parts as build it), then try measure the magnetic attraction or the revolutions per minute (RPM). [Your AP science lab kit will include the Magnetic Wire and magnets.]

Data Handling

  1. Using the weight of the moving parts and the RPM, determine the kinetic energy required to turn the motor.
  2. Using the current and voltage of your source, determine the energy delivered to the motor.
  3. Explain any difference you find between energy input and energy output.


  1. Describe your materials, equipment, an dprocedures in sufficient detail that your fellow students could repeat your experiment.
  2. Report your data. Be sure to indicate the amount of error in your measurements. For example, if you can only measure a mass of 25 gms within 1 grm, your error would be 25 ± 1, or 1/25 = 4%.
  3. Present your data in an organized form, preferably in a table, in such a way it is easy to compare results as you repeate trials or vary a specific contributing factor.
  4. Show a sample calculation, if you have calculated values.
  5. If you did a series of experiments, varying something by increasing or decreasing a factor, try to plot your data (y-axis) as a function of the factor (x-axis).
  6. You may use a spreadsheet to calculate your information and create your table.
  7. Summarize your results.
  8. Draw conclusions about what is happening.
  9. Suggest at least one way to improve your experiment.