Toys and Physics - Circular motion 1

2.1 Whirling plane

What happens
This battery-powered plane was bought from a shop in Heathrow airport. The plane is suspended from a support by the thread and switched on. The propeller at the back of the plane rotates and the plane moves in a circle. As its speed increases the radius of the circle gets bigger and the angle that the thread makes with the vertical increases.
The plane usually needs a 'push' to start it moving in the right direction.

Theory and teaching notes
This toy can be used to investigate the theory of circular motion and the conical pendulum. You can measure :
(i) the radius of the orbit
(ii) the time for a number of orbits and hence the time for one orbit
(iii) the angle that the thread makes with the vertical
(iv) the speed of the plane
(v) the mass of the plane
(vi) the tension in the thread by the addition of a Newton meter

2.2 Dragonfly

What happens
The same principles of circular motion can be shown using the dragonfly. This moves in a circle as its wings flap!

Theory and teaching notes
Same as for the plane.

2.3 Hamster in a globe

What happens
This battery powered hamster moves within the plastic sphere. As the hamster moves the sphere rolls along.

Theory and teaching notes
This toy can be used to show circular motion and Newton's Third Law. As the wheels on the hamster rotate the sphere moves ion the opposite direction.

2.4 Gyroscope

What happens
A toy gyroscope is an essential part of a set of Physics toys. The theory of the simple gyroscope can be demonstrated with one of these. It can be balanced on a small point or on a string and tilted during rotation to show precession

Theory and teaching notes
The gyroscope can be sued to demonstrate:
(a) rotational stability
(b) conservation of angular momentum
(c) precession

2.5 Coathanger

What happens
Pull open a wire coat hanger so that it forms a square. File the end of the hook flat and then bend the hook until it points towards the opposite corner of the square. Balance a 1p coin on the hook, put one finger in the corner of the square opposite the hook and then spin the coat hanger in a vertical circle - the coin stays in place! This is a very simple but excellent demonstration of centripetal force.

Theory and teaching notes
The force of the hook on the penny always acts towards the centre of rotation. This clearly shows the existence and direction of the centripetal force on a rotating object.

2.6 Magic propellor on a stick

What happens
As the round rod is rubbed along the serrated edge of the stick the small wooden propeller spins. Holding your first finger against the rod will make the propeller spin one way but if your thumb is used it will spin in the opposite direction.

Theory and teaching notes
The serrated edge of the stick sets up two sets of vibrations within the stick as the rod is rubbed along it.

These vibrations have different amplitudes and are at right angles to each other. An elliptical pulse is set up within the rod and so the propeller rotates.

2.7 Spinning Santa

What happensAs the button is pressed the Santa spins and as its speed increases it 'splits open', revealing a snowman within it. As it slows down it closes again.

Theory and teaching notes
All objects try to move in s straight line unless a force acts on them. As the Santa's spin rate increases the springs holding its sides are not strong enough to force them to move in a small circle and so they open out to show the snowman underneath.

2.8 Yo Yo

What happens
As the Yo Yo is spun it can 'climb' the string.

Theory and teaching notes
A useful toy to show the conservation of angular momentum and its transfer to linear momentum.