# A model train, with a mass of #12 kg#, is moving on a circular track with a radius of #6 m#. If the train's kinetic energy changes from #120 j# to #36 j#, by how much will the centripetal force applied by the tracks change by?

##### 1 Answer

Jun 1, 2016

#### Explanation:

The centripetal force is defined as

The kinetic energy is defined as

So we can express the force as the energy writing

The initial force can be calculated with

The final force can be calculated with

The difference of centripetal force is

The negative sign is because the train is reducing the speed and then the centripetal force is reducing.