Question

A model train, with a mass of `8 kg`, is moving on a circular track with a radius of `2 m`. If the train's kinetic energy changes from `8 j` to `48 j`, by how much will the centripetal force applied by the tracks change by?

Answer 1

I found that it changes of `40N`

Explanation:

I can use the definition of Kinetic Energy: `K=1/2mv^2`
`K_i=8=1/2*8v_i^2`
`v_i=sqrt(2)m/s`
`K_f=48=1/2*8v_f^2`
`v_f=sqrt(12)m/s`

We know that centripetal force is: `F_c=mv^2/r`
so:
`F_(ci)=mv_i^2/r=8(2)/2=8N`
and:
`F_(cf)=mv_f^2/r=8(12)/2=48N`

`DeltaF_c=48-8=40N`