The best physics experiments for kids need no equipment budget — a ruler, a ball, a glass of water, and some cardboard cover an enormous amount of territory. Below are ten, grouped by concept, each with what is happening and one variable you can change to turn it into a real experiment.
Forces and Motion
1. Balloon Rocket
Tape a balloon to a straw threaded on a long string strung across a room. Inflate, pinch, release. It shoots along the string.
Why: Newton’s third law — air rushes out one way, the balloon is pushed the other way. This is how rockets work, and the balloon is a genuinely accurate model.
Variable: how much you inflate it. Does more air mean more distance?
2. Marble Ramp
Prop a ruler or a piece of cardboard as a ramp. Roll a marble down and measure how far it travels along the floor. Change the ramp height.
Why: gravitational potential energy converts to kinetic energy. Higher start, more speed.
Variable: ramp height versus distance travelled. This one graphs beautifully.
3. Friction Test
Slide a toy car down the same ramp onto carpet, then tile, then cardboard. Measure how far it goes each time.
Why: friction converts motion into heat. Rougher surfaces have more of it.
Variable: surface type. Predict the order before you test.
4. Egg Drop
Drop a raw egg from increasing heights onto a padded contraption you build — straws, bubble wrap, cotton, parachutes.
Why: the egg stops over a longer time and distance, so the force on it is lower. This is impulse, and it is why cars have crumple zones.
Variable: padding material or drop height. Do it outside.
Air and Flight
5. Paper Plane Aerodynamics
Build three different designs and fly each five times. Measure distance and consistency.
Why: lift, drag, and centre of mass. Narrow wings go far; wide wings glide slowly.
Variable: wing shape. Five flights per design because one flight proves nothing.
6. Blowing Between Two Papers
Hold two sheets of paper a few centimetres apart and blow between them. They move together, not apart.
Why: fast-moving air has lower pressure than slow air — Bernoulli’s principle. The higher pressure on the outside pushes them in.
Variable: how hard you blow, or how far apart you hold them.
Sound
7. Water Glass Xylophone
Fill glasses with different amounts of water and tap each with a spoon.
Why: more water means more mass to vibrate, so lower pitch. The glass with the most water is the lowest note.
Variable: water volume versus pitch. Try to play a simple tune to prove you can control it.
8. String Telephone
Two paper cups, a long string, ends poked through and knotted. Pull it taut and talk into one cup.
Why: your voice vibrates the cup bottom, the string carries the vibration, the other cup vibrates the air. Slack string kills it — tension is required.
Variable: taut versus slack, or string material.
Light and Water
9. Broken Pencil
Put a pencil in a glass of water at an angle. It looks bent or broken at the waterline.
Why: light changes speed entering water, so it bends — refraction. Your brain assumes light travelled straight.
Variable: angle of the pencil, or try oil instead of water.
10. Ping Pong Ball in a Hair Dryer
Point a hair dryer straight up (cool setting) and balance a ping pong ball in the airflow. Tilt it — the ball stays.
Why: the fast air column has lower pressure, so the surrounding higher pressure keeps the ball inside the stream. This is the Bernoulli principle again, and it is the same effect that generates lift on a wing.
Variable: how far you can tilt before the ball falls. Adult supervision for the hair dryer.
How to Make These Count as Experiments
Every one of these physics experiments for kids can be done in under an hour.
The pattern that works for all ten:
- Predict before you test, and write the prediction down
- Change exactly one thing
- Repeat at least three times and average
- Measure in numbers — centimetres, seconds, not “far” and “fast”
- Explain what happened in your own words
Step one is the one that matters most. A wrong prediction followed by “interesting, I thought the opposite because…” is far better science than a right guess with no reasoning.
Related Reading
- Newton’s laws of motion — the theory behind numbers 1-4
- What is gravity? — why the marble comes down at all
- Science fair project ideas — if you need something bigger
