Squeeze a coin or nut through the opening of the balloon, make sure that the coin or nut goes all the way in.
Blow up the balloon and tie its end.
- Hold the balloon in one hand.
- Swirl the balloon whilst keeping it in your hand. The coin may bounce at first, but you should find that it will start to roll around inside the balloon.
- Stop swirling the balloon. You should see that the coin continues to roll, inside the balloon, for several seconds. Why?
Does the size of the coin matter? Repeat the experiment with different sized coins.
Repeat the experiment again with the metal nut. As the edges of the nut strikes the inside of the balloon the rubber will vibrate, creating a whirring sound.
Try spinning the balloon at different speeds, what happens?
Get the Unit of Work on Forces here!
- Push, pull
- Friction & spin!
From inertia to centripetal force, this unit covers many concepts about Newton’s Laws!
Includes cross-curricular teaching ideas, student quizzes, a sample marking rubric, scope & sequences & more
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Why Does This Happen?
Isaac Newton’s first law of motion said that anything that is moving will want to keep moving in a straight line unless another force acts against it. This is called inertia.
The coin travels around the outside of the balloon because of inertia, i.e. it’s trying to travel in a straight line but the curved surface of the balloon swings it around the corner. The coin continues to travel around the balloon until gravity and friction slows it down.
The same principle applies to motorbike stunts in circular cages and rollercoasters!
Variables to test
- Try different speeds of rotation
- Does it matter as to the size of the balloon?
- Teaching about Newton’s laws? Check out the Forces, Friction & Movement workshop!
Get in touch with FizzicsEd to find out how we can work with your class.
Forces, Friction & Movement
Years K to 6
Maximum 30 students
School workshop
60 or 90 minutes
Online Class Available
STEM Full Day Accelerator - Primary
Designed from real classroom experiences, this modular day helps you create consistently effective science learning that directly address the new curriculum with easily accessible and cost-effective materials.
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