A model train, with a mass of #3 kg#, is moving on a circular track with a radius of #2 m#. If the train's kinetic energy changes from #32 j# to #12 j#, by how much will the centripetal force applied by the tracks change by?

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Answer 1 · 2017-04-10T09:30:17

The centripetal force changes by #=20N#

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 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#

#=2/2*(32-12)N#

#=20N#