KE - Kinetic Energy


KE - Kinetic Energy

Kinetic energy is the energy it takes to accelerate a mass up to speed. The energy is proportional to the square of the speed.

It is not always obvious which energy is kinetic energy.

The next pages look at:


Heat - the energy is stored in the kinetic energy of molecules

Compressed gas - again, the energy is stored in the kinetic energy of gas molecules.

KE = 1/2 mV2

High speed train

Let's see what kineic energy means to a train. An old train needed several steam engines to pull it up a hill.

High speed trains do not because they have so much kinetic energy..

A steam engine traveling at 60 kM/h. has enough kinetic energy to coast up a slope to a height of 14 metres.

However, if a train was traveling at 300 kph, then a 14 metre hill would only slow it by 6 kph.

A high speed train does not need several locomotives to get it up a hill. At 300 kph it has enough stored  kinetic energy to coast up anything to a height of 350 m.

Wind Energy etc

Wind energy is kinetic energy

As is wave energy.

Tidal Energy

Tides are using the kinetic energy of the moon.

Once they have taken it all, the moon will crash into the Earth.

Not exactly renewable!


The heat in the earth is due to movement of the molecules. Half from radioactive decay, and half from the collisions of the particles falling together to form the Earth.