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Inertia egg experiment

You will need:

  • 1 x Drinking glass, three-quarters full of water
  • 1 x Sheet of newspaper
  • 1 x cardboard toilet roll
  • 1 x Plastic tray or plate (This piece of equipment must cover the glass, be flat on the bottom and have a raised lip around the top)
  • 1 x Egg (if a student has egg allergies you can change this to a water bomb instead)

    Inertia egg experiment materials on a chopping board;cardboard toilet roll, egg, plastic lid and glass of water
    Easy to get materials to make this rubber band racer!

egg on toilet roll over a glass for a inertia experiment
Can you get the egg into water in one smooth movement?


  1. Place the newspaper on the table, to stop the splashing water getting the table wet.
  2. Place the glass of water in the middle of the newspaper.
  3. Place the tray/plate on top of the glass, and stand the toilet paper roll on top of it. Note: Make sure the toilet paper roll is directly above the glass of water. We don’t want our egg to hit the table instead of the water!
  4. Add your egg on top of the toilet paper roll. Use a water bomb if there a egg allergies in the room.

    egg on toilet roll over water glass for inertia experiment
    Ready for a karate chop!
  5. Now for the tricky part. You need to very quickly knock the tray/plate sideways, using a kind of “sideways karate chop” technique. The tray will fly horizontally, and the raised lip on the edge will catch the toilet roll, and the egg should fall straight down into the water, and stay un-cracked!

    Variation: Try this experiment without the water in the glass!

Why does this work?

Isaac Newton’s First Law of Motion says that an object that’s moving will continue to stay moving, and one that’s stationary will continue to stay still, unless a new force is applied to it.

  1. While the egg is balancing on the toilet roll, the egg isn’t moving and so it wants to remain that way.
  2. When you knock the tray sideways, you apply a force that moves it quickly out of the way.
  3. The raised lip on the tray transfers this force to the toilet roll and it too flies sideways.
  4. At this point, the egg is still stationary for just a split second, until gravity gets a hold of it and pulls it down into the glass.

This is the same principle that makes the classic magic trick, where a magician whips a tablecloth off a table leaving the crockery and cutlery still there, work.


Inertia (the tendency of moving objects to stay moving) it critical to understand when you’re thinking about road safety. Without seatbelts in our cars, our bodies would keep moving forwards if our car stops suddenly, for example in a crash. The seatbelt applies a force to our bodies that slow them down, stopping us going flying. The same goes for loose objects that are hanging around in the back seat of your car - an unrestrained object can move forwards in a car crash and can become a projectile

Up for a challenge? Try this experiment with a bigger tray, and two toilet rolls, eggs and glasses. Try three, maybe four!

Be Amazing Book Front Cover; Ben Newsome, teacher & founder of Fizzics Education. Be Amazing -how to teach science the way primary kids love
Be Amazing!
How to teach science, the way primary kids love

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