Home > Physics > Circular Motion

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?

Answer 1

Nathan Ashcroft

#8# Newtons

The train's speed before and after the kinetic energy change can be found using the following kinetic energy formula:

#v=sqrt((2E)/m)# #-> v = sqrt((2*16)/2)=sqrt(16)=4#

So we know the train was travelling at #4 ms^-1#

The kinetic energy at the end is #0J# so the train has obviously came to rest.

The centripetal force required at #4ms^-1#:

#F = (mv^2)/r# #-> F =(2*(4^2))/4=8N#

And the centripetal force required when the train is at rest is just #0N#. Thus the change in change in centripetal force is #8-0=8N#

By signing up, you agree to our Terms of Service and Privacy Policy

Answer 2

Lily Adams

The centripetal force applied by the tracks will change by 16 Newtons.

By signing up, you agree to our Terms of Service and Privacy Policy

Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.