A model train, with a mass of #15 kg#, is moving on a circular track with a radius of #6 m#. If the train's kinetic energy changes from #81 j# to #27 j#, by how much will the centripetal force applied by the tracks change by?
The centripetal force has decreased by
This question is about circular motion and how much centripetal force is being applied, which is given by the equation:
Now, instead of solving for the velocity (and needing to take a square root, just to have to square it again, let's solve for the term
substituting then gives
We are looking for the change in centripetal force which we can write as:
Therefore, the centripetal force has decreased by
Note: The question had given us more information than we actually used - the mass was redundant since the kinetic energy alone was sufficient information. Other versions of this question may not include the mass.