What forces are involved when objects move in a circular motion? Starter Sketch a diagram of the roundabout and draw on the forces that act on a car.

Glossary Centripetal force – the resultant force towards the centre of a circle acting on an object moving in a circular path.

Watch these clips – write down anything of interest Fair ground ride G force training Why do these objects move in a circle?

Demo – spinning object Spin an object, let go , moves in a tangential way.

The object is accelerating towards the centre of the circle. An object moving in a circular motion at a constant speed, will have a constantly changing velocity. The change of velocity is towards the centre. The object is accelerating towards the centre of the circle. The velocity is directed along a tangent to the circle. Note: Accn = change in velocity / time

Acceleration Accn = the change in velocity / time Therefore – acceleration is continually increasing towards the centre of the circle. BE CAREFUL! The acceleration changes the direction not the speed.

Task: Centripetal Force Swing a small bung on a string around your head then try a big bung. Can you feel the difference?! What has increased? NOW – try 1 size of bung with a short piece of string then a long piece. What has changed?

Factors affecting centripetal force Radius of circle Mass of object Speed of rotation A greater mass gives a greater centripetal force. Decrease the radius and increase the centripetal force.

Have a go at the questions

The bucket of water trick