A measurement of the local gravitational acceleration.

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Teachable Topics:

  • Newton's Laws
  • Acceleration
  • Gravity


A body of mass will fall at a constant acceleration due to the attraction of mass between the body and the mass fo the earth. If the acceleration is labeled g, then we can write:

F = mg

where m is the mass and F is the force the earth exerts on it.

Since acceleration is the result of the change in velocity (Δv) with the passage of time (Δt),


  • Ruler
  • 12V DC power supply
  • Photogate
  • steel ball
  • Three clamps
  • Vernier caliper
  • Scissor jack
  • Electromagnet
  • Alignment string
  • Four connecting wires

Timed Free Fall Experiment


  • Once the equipment is clamped in place, align the photogate with the electromagnet. This is done using an alignment string, which hangs from the electromagnet, (See photo).
  • After it is aligned, remove the string, and adjust the strength of the electromagnet so the metal ball is hanging from the top.
  • Then reset your photogate before dropping the ball through.
  • Repeat this three times, adjusting the height each time.

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