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Egg and Broom Trick

Students will watch an impressive (and potentially messy!) demonstration of inertia.

Here, an egg is supported over a glass of water by a toilet paper tube. When the supporting tube is moved away quickly, the egg drops straight into the cup.

How?

The explanation has to do with inertia. Very little sideways force is applied to the egg as the tube is quickly knocked out of the way. The only force left to act on the egg is gravity, so the egg drops straight down.

Objectives

  • Describe a scenario that demonstrates the property of inertia.

Materials

  • Per Demo or Group:
    Egg
    Toilet paper tube
    Non breakable baking pan, plate, or tray: 8 x 8 cake pan or aluminum pie plate work well.
    Glass with a diameter at least as large as the egg, half filled with water
    Broom with long bendable bristles

Key Questions

  • What forces are acting on the resting (i.e. non-moving) egg?
  • What forces are acting on the egg when the paper tubes are knocked out?
  • How can the inertia of the egg explain what happened?

What To Do

  1. Set a glass, half full of water, near the edge of a table. Place the baking pan on top. The edge of the pan should stick out over the edge of the table.
  2. Stand the toilet paper tube upright on the baking pan so that it is directly over the glass of water.
  3. Place the egg on the end of the toilet paper tube. Depending on the diameter of the tube, you may want to place the egg on its’ side so that it doesn’t fall inside.
  4. Stand the broom vertically against the table. Place your foot on the bristles, and pull back on the handle (like a catapult).
  5. Let go! The broom will hit the pan, knocking it and the tube out of the way and the egg will drop into the water. Watch this video to see how it’s done.

Extensions

  • Try replacing the egg in this experiment with heavier and lighter objects. Can you still get the trick to work?
  • How can the inertia of the egg explain what happened

Other Resources

Science World | Youtube | Inertia