You will need
- 1x cup of corn starch/ cornflour.
- ¼x cup of water.
- One glass jar or another sealable round container.
- Wide plank of wood for the ramp.
- Small cardboard box for the ramp.
- One ping pong ball or golf ball.
Put 1 cup of corn starch/ cornflour in the glass container slowly add water to the cornflour while mixing with a spoon (aim for about ¼ cup of water). The mixing is done when the liquid has the texture of honey.
Add the ping pong ball or the golf ball into the corn starch mixture.
Seal the jar tightly. You may want to add tape around the seal to ensure that you don’t leak your experiment everywhere!
Set up a ramp using the cardboard box and plank of wood.
Start rolling! Try different angles to see if the motion of the roller changes. What do you observe?
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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What is going on?
An objects’ centre of mass is the point where its mass is equally balanced. When an object rolls, it rolls about its centre of mass.
Since the jar has a ping pong ball its density is inconsistent (non-uniform). This means that the centre of mass isn’t actually in the middle of the jar, especially as it keeps moving! While the jar is rolling the ping pong ball being less dense than its surrounding attempts to float. This results in the jar moving in one direction while the ball attempts to move in the opposite direction. This produces the rocking motion that you see on the ramp.
This ‘stir-thickening’ of the cornflour slime shows that the material is a Non-Newtonian fluid, which means that the material does not follow the properties described of fluids by Newton’s law of viscosity which defines the relationship between the sheer stress to sheer rate of a liquid at a given temperature and pressure (in the case of a Non-Newtonian fluid, the viscosity is not constant and is dependent on the sheer rate i.e. in this case, the amount of pressure applied).
Variables to test
More about variables here
- Can you recreate this effect using plain water? Why or why not?
- Does the slope of the ramp change how the jar rolls?
- Can the effect be recreated using denser objects like large marbles instead of ping pong balls?
- Why not try and see if multiple ping pong balls (you may need a larger jar for this one).
How can this science be used?
Non-Newtonian fluids can be handy! Plenty of research is being done about how to use this special material in modern technology. Local and international scientists as well as engineers have been developing liquid body armour using non-Newtonian fluids, since they are really good at stopping bullets!
In 2010 a number of articles were released about the development of a speed bump dynamically changed depending on how fast cars were travelling over it! If you travel over the speed bump at a slow speed the fluid inside the speed bump would move out of the way and you’d barely feel the speed bump. However, if you travel over the speed bump too fast the speed bump would react quickly to the increased force and become almost solid… making your car bounce and reminding you to slow down!
Forces, Friction & Movement
Years K to 6
Maximum 30 students
School workshop
60 or 90 minutes
Online Class Available
Hands-on Kids Science Party
>20 hands on science experiments
Gigantic bubbles
Slime making
Professional science show
From $395 inc. GST
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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