Explanation

Aside from nuclear reactions energy is neither created or destroyed but is converted between different forms.

This demo shows how a vehicle going up and down a hill changes energy between forms in the journey.

The journey consists of the following stages and conversion.

• In order to climb the first hill the vehicle uses either chemical (petrol or diesel) or electrical energy to increase its potential energy.
• Whilst parked at the top of the hill it retains this potential energy until its brake is released and it starts rolling down the hill converting potential energy to kinetic energy.
• At the bottom of the hill it no longer has any potential energy but has enough kinetic energy to get it to the top of the smaller hill.
• As it climbs the smaller hill some of this kinetic energy is converted to potential energy.
• At the top of this smaller hill it has both potential and kinetic energy. It still has kinetic energy left over as the second hill is smaller than the first.
• As it rolls down this second hill it converts all of its potential energy to kinetic energy by the time it reaches the bottom.
• It then contiues along the road using it remaining kinetic energy.

Throught the whole of this journey energy is being lost through friction (wind resistance, tyres on the road,axle friction etc) and sound energy.