# A model train, with a mass of #2 kg#, is moving on a circular track with a radius of #4 m#. If the train's kinetic energy changes from #16 j# to #0 j#, by how much will the centripetal force applied by the tracks change by?

##### 1 Answer

Mar 1, 2016

#### Explanation:

We can use kinetic energy formula to get the speed of the train before and after the kinetic energy change:

So we know the train was travelling at

The kinetic energy at the end is

The centripetal force required at

And the centripetal force required when the train is at rest is just