Here are a couple of fun inertia science experiments for kids that go perfectly with a unit on force and motion, and you probably have all the supplies on hand that you’ll need for them!

Both of these science experiments demonstrate inertia. Inertia is summed up in Newton’s First Law of Motion, and is an object’s resistance to a change in motion. An object in motion stays in motion and an object at rest stays at rest unless an outside force acts on it. This means that objects also resist a change in speed or direction.

Note: These science experiments are actually demonstrations, because we are not testing a variable. They are hands-on activities that demonstrate the concept of inertia so that kids understand it. Just thought I’d clarify!

Inertia Science Experiment #1: Penny Stack

Find some pennies. Stack 5 pennies and grab one more to use as the shooter. Flick one penny toward the stack. Give it a good, solid flick.

Kids may expect that the stack will fall over when the penny hits the stack, but this is not the case!

The one penny will transfer its energy to the penny at the bottom of the stack, which will then zoom forward. The rest in the stack will stay right where they were because an object at rest stays at rest unless acted on by a force!

Inertia Science Experiment #2: Penny Dunk

Make a stack of pennies land in a glass of water with this fun science experiment! The concept behind this is the same as the old-fashioned trick of yanking a tablecloth out from under a place setting of dishes… except that it’s a lot less messy if something goes wrong.

Place an index card on top of a glass of water. It’s best if you have a clear glass so that kids can see what’s happening inside.

Give the index card a firm flick. It will fly away while the pennies just drop straight into the glass.

Kids may expect the pennies to fly off with the index card. However, they actually stay in the same place because of inertia. They are objects at rest staying at rest! Force is applied to the index card, so it moves. The pennies drop straight down into the water once the card is no longer there to hold them up!

It may take a few tries to flick the index card just right, but once kids get the hang of this, they’ll definitely want to try it more than once!

Need more science experiment ideas?

Don’t Melt the Ice! Challenge kids to design a container that will keep an ice cube from melting for the longest possible time.

Science Experiments with Hot Wheels Cars – True science experiments that test air resistance and the effect of mass on acceleration.

1. ##### Sherry Jul 31, 2019

Thank you for the penny experiment. Will do with my granddaughters.

2. ##### Caroline Mar 30, 2020

good experiments! it took me a couple tries on that second one but soon got the hang of it! thank you!

3. ##### Sheldon Katz Apr 15, 2020

Good experiments that I will perform for my young grandchildren. When I was teaching physics in a college lecture hall I would use a place setting of china that I had received for free and build up a small tower, placing a ping pong ball in the center of an inverted soup bowel. The small tower of china was placed on a silk-like material, that could be snapped from the china tower without losing the ping pong ball or any dishes. Having lost my "props", I will use your method to teach my grandchildren. Thanks for posting this.