A model train, with a mass of 8 kg8kg, is moving on a circular track with a radius of 1 m1m. If the train's rate of revolution changes from 3/8 Hz38Hz to 5/4 Hz54Hz, by how much will the centripetal force applied by the tracks change by?

2 Answers
Mar 10, 2018

We know that angular frequency omegaω and natural frequency nuν are related as, omega =2 pinuω=2πν

So,if the angular frequency changed from omega_1ω1 to omega_2ω2

we can say, omega_2 =2pinu_2=2pi(5/4)=7.854 rads^-1ω2=2πν2=2π(54)=7.854rads1 and omega_1=2pinu_1=2pi(3/8)=2.355 rads^-1ω1=2πν1=2π(38)=2.355rads1

Now,centripetal force is expressed as momega^2rmω2r

So,change in centripetal force is mr(omega_2^2 - omega_1^2)=8*1*(7.854^2-2.355^2)=449.113 Nmr(ω22ω21)=81(7.85422.3552)=449.113N

Mar 10, 2018

The change in centripetal force is =449.1N=449.1N

Explanation:

The centripetal force is

F=(mv^2)/r=mromega^2NF=mv2r=mrω2N

The mass of the train, m=(8)kgm=(8)kg

The radius of the track, r=(1)mr=(1)m

The frequencies are

f_1=(3/8)Hzf1=(38)Hz

f_2=(5/4)Hzf2=(54)Hz

The angular velocity is omega=2pifω=2πf

The variation in centripetal force is

DeltaF=F_2-F_1

F_1=mromega_1^2=mr*(2pif_1)^2=8*1*(2pi*3/8)^2=44.4N

F_2=mromega_2^2=mr*(2pif_2)^2=8*1*(2pi*5/4)^2=493.5N

DeltaF=F_1-F_2=493.5-44.4=449.1N