You will need
- A Coke bottle or any other plastic screw-top bottle (the smaller the better)
- Uncooked Rice
- A pencil or chopstick or any other straight rod
Fill the bottle with uncooked rice.
Plunge the pencil straight down into the bottle. Try to lift the bottle just by the pencil. Doesn’t work too well…
Now try plunging the pencil in and out at least 30 – 40 times at different heights for compaction.
Can you now lift the bottle off the table just using the pencil? Why does this work?
This experiment is worth running over a large bowl to catch any mess!
Troubleshooting
Doesn’t work? Try putting the pencil into the rice at different heights each time.
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
The more contact between two surfaces, the great the friction. When you push the pencil in and out of the rice you are slowly compacting the rice and pushing air out of the container. This means that more and more rice gets in contact with your pencil which slowly but surely increases the friction between the rice and the pencil. Eventually, there is so much friction you can lift the rice-filled jar, or bottle, into the air as the frictional forces are greater than the force of gravity.
Road safety application
Friction all about contact, something that you definitely want when it comes to your tyres! Friction allows you to transfer forces from your vehicle to the road surface, allowing you to change direction, accelerate and brake. Regularly check the condition of your tyres, ensuring that they have enough tread to disperse water (to keep you in contact with the road) as well as that they are inflated to the correct pressure.
Variables to test
- Try different types of rice.
- Try different widths of pencils & sticks… which is the optimal size?
- Is it possible to perform the same demonstration using sand or gravel in the bottle?
- 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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