Toys and Physics – Mechanics

6.1 Walking monkey and teeth

What happens
When the toy is wound up it 'walks' along the floor – in the case of the teeth they also open and close.

Theory and teaching notes
An example of the conversion of stored energy in the spring to motion energy as the toys walks and vibrates.

6.2 Elastic powered seed

What happens
The seed is fired into the air using the stick and elastic band. As it falls it spins.

Theory and teaching notes
The stored energy in the elastic band is converted to potential and kinetic energy as the "seed" rises and then falls back to the ground.

6.3 Inertia powered cars

What happens
This particular inertia powered machine was bought in Angouleme in France. The flywheel is set rotating by pulling the car backwards on the floor. As soon as the flywheel is spinning rapidly the car can be let free to travel off on its own.

Theory and teaching notes
Incorrectly called a friction car the machine is driven forward as the rotational kinetic energy in the flywheel is transferred to the linear kinetic energy of the car.

The second photograph shows another vehicle – also wrongly called a friction powered car.

The car has a small flywheel inside it. The flywheel is given energy by rubbing the back wheels on the carpet – hence the inaccurate name of friction powered car. This energy is then transferred by gear wheels to the driving wheel of the car.

6.4 Woodpecker

What happens
When the woodpecker is given a slight push it moves jerkily down the rod, pecking at it as it goes.

Theory and teaching notes
The hole in the bead holding the woodpecker is a little larger than the rod. When the woodpecker is horizontal the hole in the bead is vertical and the bird slips down a little. As soon as the woodpecker moves up or down on its spring the hole moves out of a vertical line and so sticks on the rod and so on. This stick-slip motion gives the woodpecker its jerky movement.

6.5 Water pistol

What happens
When the trigger is pressed a jet of water shoots out!

Theory and teaching notes
The pressure on the outside of the pistol forces water out at high speed through the small nozzle. A small reduction of the reservoir volume ejects a narrow but rapidly moving jet.

6.6 Tin boat

What happens
A little water should be poured into the small boiler in the centre of the boat through one of the tubes at the stern. A small piece of firelighter is placed in the pan below the boiler in the boat and lit. The boat moves through the water.


Theory and teaching notes
The water in the boiler boils and steam is produced. This goes out of one of the tubes – the chances of the amount of water in the tubes being the same is very low. This small jet of air pushes water with it and the combined effect pushes the boat along. Water is drawn in through the other tube to replenish the boiler. Motion with no moving parts!

6.7 Clockwork mouse

What happens
When the mouse is wound up it moves along, wagging its tail.

Theory and teaching notes
The stored energy in the spring is transferred to kinetic energy in the mouse. It is most important to have at least one clockwork toy in the collection. They can also be used to show that the energy is dissipated as heat due to friction and so this limits the distance that the toy can travel.