Fix Santa’s sleigh wheels
Santa Claus has been experiencing some bumpy roads lately when he drives his sleigh on the ground. This doesn’t help him to travel quietly on land plus it may cause damage to the gifts he’s carrying. Help him out by finding the best shape for his sleigh wheels to reduce the bumps. We know that the normal wheel is round, but wheels can be different and can adapt to the ground the vehicle is travelling on.
In today’s activity, we are going to test out what shape should the wheels be for our special terrain. We’re going to make a specific bumpy road and find the best shape for the sleigh wheels according to these bumps.
Get your materials ready!
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Try it out!
Step 1
Let’s start off by making our bumpy road. We’ll do this by taking a bunch of toilet paper rolls and stick them next to and touching each other on a flat piece of cardboard.
Step 2
Let’s make the sleigh’s chassis. Take a rectangular piece of cardboard and attach two pieces of straws to its bottom, one at the front and one at the rear. The straw will be the shaft for the wheel axles. Insert a kebab stick in each straw and these will be the axles. Attach a paper clip to the front of chassis and tie a piece of string to the paper clip. This will help you pull the sleigh on the track you created in step 1.
Step 3
Now let’s talk wheels. The traditional shape for a wheel is a circle. But we are now going to test out the best shape for a smooth ride on our special bumpy track. Cut out your cardboard pieces into different shapes. We chose squares, circles, triangles, and customised shape to fit our track.
Step 4
Once you have a set of wheels you can test them out. Attach the wheels to the sleigh using kebab sticks, one shape at a time or create multiple sleighs with different wheels.
Place the sleigh on the track and pull the string for it to move. you can compare which wheel is most effective by testing the sleigh also on a flat surface.
Which shape provided you with the smoothest ride?
Does the shape move the sleigh better on a flat surface or the track? Which one?
Take it further!
In this test you should realise that the round wheel is the worst wheel, and the square wheel is the best. What?! Yep, that’s right. This works because, as the cart rolls, the vertical distance from each axle to the horizontal base of the road stays about the same. Study the cart carefully as it rolls, and you’ll see that the axle neither rises nor falls: High spots in the lumpy road are exactly cancelled by flat spots on the square wheel.
This does not mean that the square wheels are the best wheels ever. They are only the best to provide a smooth ride on a road made from circles, or catenary curves to be mathematically specific.
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