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?
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.