Cheese Rolling – Gravitational Potential Energy to Kinetic
Funny really as I always think of this as a simple topic. However, my students always find it hard, especially the formulae.
First place to start is the hill near to the village (Brockworth) where I grew up where they still do Cheese Rolling every year… http://www.cheese-rolling.co.uk/index1.htm. Even my primary school teacher wrote a book on the topic. (However, it is not focused on the Physics!)
So now you have the idea think about a man who lifts a cheese and himself up to the top of a hill. His muscles have to do work as he is moving himself and a cheese to a point further away from the surface of the Earth. This is because the man and cheese are in the influence of a “gravitational field” which causes anything with mass to feel weight or acceleration towards the centre of the object.
So the formulae we employ to work out the work done in climbing the hill is the change in height x distance moved against the field x mass. #
We often write this as…
Ep = mgh or sometimes as mgΔh to show “a change in height”.
So where has the energy come from…. well simple the muscles in the body of the man have contracted and converted chemical energy to movement energy to push the man away from the field.
So what happens to the energy as you release the cheese? Well we think of another idea of “kinetic energy”. As you roll down the hill and gain in velocity you exchange your gained Ep to Ek so then most of the energy is coverted according to the rule ½ mv2 .
Often we write that mgΔh = ½ mv2 so if it was a 100% transfer we could work out the maximum velocity of a cheese falling down the hill!
Try out these animations in flash to help you out…