A model train, with a mass of #9 kg#, is moving on a circular track with a radius of #15 m#. If the train's kinetic energy changes from #72 j# to #36 j#, by how much will the centripetal force applied by the tracks change by?

1 Answer
Aug 21, 2017

Answer:

The change of centripetal force is #=4.8N#

Explanation:

The centripetal force is

#F=(mv^2)/r#

The kinetic energy is

#KE=1/2mv^2#

The variation of kinetic energy is

#Delta KE=1/2mv^2-1/2m u^2#

#=1/2m(v^2-u^2)#

The mass is #m=9kg#

The radius is #r=15m#

The variation of centripetal force is

#DeltaF=m/r(v^2-u^2)#

#DeltaF=2m/r1/2(v^2-u^2)#

#=(2)/r*1/2m(v^2-u^2)#

#=(2)/r*Delta KE#

#=2/15*(72-36)N#

#=4.8N#