A model train, with a mass of 6 kg6kg, is moving on a circular track with a radius of 2 m2m. If the train's rate of revolution changes from 2 Hz2Hz to 6 Hz6Hz, by how much will the centripetal force applied by the tracks change by?

1 Answer
Oct 9, 2017

The force will change by 15150N15150N

Explanation:

The equation for centripetal force is

F_c = (mv^2)/r = momega^2rFc=mv2r=mω2r

where vv is linear velocity, omegaω is angular velocity, rr is radius and mm is mass.

We know that the mass is 6kg6kg and the radius is 2m2m. We will use angular velocity for these calculations, but we could equally do it with linear velocity.

We know that

omega = 2pifω=2πf

where ff is the frequency, which we have.

For f = 2Hzf=2Hz

then

omega = 2pi*2 = 12.6"rad"/"sec"ω=2π2=12.6radsec
F_c = 6 * 12.6^2 * 2 = 1905NFc=612.622=1905N

whereas with f = 6Hzf=6Hz

omega = 2pif = 2pi * 6 = 37.7 "rad"/"sec"ω=2πf=2π6=37.7radsec

so

F_c = 6 * 37.7^2 * 2 = 17055NFc=637.722=17055N

Therefore the centripetal force will change by

DeltaF_c = 17055N - 1905N = 15150N