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

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Answer 1 · 2017-08-21T06:23:54

The change of centripetal force is $= 4.8 N$ $=4.8N$

The centripetal force is

$F = \frac{m v^{2}}{r}$ $F=(mv^2)/r$

The kinetic energy is

$K E = \frac{1}{2} m v^{2}$ $KE=1/2mv^2$

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

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

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

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

$=(2)/r*Delta KE$

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

$=4.8N$

A model train, with a mass of 9 kg9kg9 kg, is moving on a circular track with a radius of 15 m15m15 m. If the train's kinetic energy changes from 72 j72j72 j to 36 j36j36 j, by how much will the centripetal force applied by the tracks change by?