Inertia is Newton’s first law. It states that an object in motion tends to stay in motion and an object at rest tends to stay at rest.  Inertia is the word we use to explain this phenomenon.

An experiment on inertia and how Newton's First Law works.

Inertia Experiment

Get a wheeled toy, like a car or a truck and place an object on top of it, like a penny or lump of clay. Send the car down a short ramp and have it crash into an object at the bottom.  The car will stop, but the penny or lump of clay will shoot forward.


Ask your kids questions about it:

  • Why does the clay keep moving when the car stops?
  • Why does the car stop?
  • Does this work no matter the size and speed of the car? (experiment with different conditions)
  • Is this true of real cars out on the road? Why do you think we wear seat belts?

Additional Layers

  • You know that trick where magicians pull a tablecloth from under a fully set table? It’s not magic, just physics! Try some magic tricks yourself.
  • I had a science professor in college who said that people who rode in the beds of trucks or didn’t wear seat belts, didn’t understand physics. What do you think he meant?
  • Read up more about Isaac Newton and his life.
  • Isaac Newton proposed a series of rules or theories about physical properties, these became so accepted that they became known as Laws. We call them Newton’s Laws even today. But Einstein proved that Newton’s Laws weren’t in fact correct. They’re good enough for physical properties on a normal scale here on earth, but in micro scales of atoms or macro scales of outer space, they are inadequate. Discuss the difference between a scientific theory and a scientific law. Talk about how science is always refining and perfecting human knowledge of the universe, but that we actually still know very little.

Unit 1-1 Free



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