demonstrations:gear_ratios

Gear Ratios

Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Simple Machines

Alternative titles: Gears as Simple Machines

Summary

Gears are wheels with teeth that fit together to transfer motion, change speed, or change direction. By connecting large and small gears, you can build a gear train to explore how gears make work easier.

Procedure

  1. Print and color a gear pattern.
  2. Tape the pattern to a Styrofoam tray and have an adult cut out the gears.
  3. Pin the gears to a piece of cardboard so their teeth fit together.
  4. Turn the big gear slowly and watch how the small gear moves.
  5. Mark each gear with a colored dot at the top, then count how many turns each gear makes as you spin the big gear.
  6. Optional: Add a small handle to the big gear to make it easier to turn.

Variations

  • Use ridged water bottle caps as simple gears.
  • Try gears from building kits like LEGO or K’Nex.
  • Experiment with three or more gears to build a gear train with idler gears.

Safety Precautions

  • Have an adult cut the Styrofoam with a sharp knife.
  • Handle thumbtacks or pins carefully to avoid injury.

Questions to Consider

  • Why does the small gear turn faster than the big gear? (Because the smaller gear has fewer teeth, it makes more rotations per turn of the big gear.)
  • Why do the gears turn in opposite directions? (Because the teeth push against each other in reverse.)
  • How do gears make work easier? (They allow you to trade force for speed, or change the direction of motion.)