A model train, with a mass of $4 k g$ $4 kg$ , is moving on a circular track with a radius of $3 m$ $3 m$ . If the train's kinetic energy changes from $15 j$ $15 j$ to $6 j$ $6 j$ , by how much will the centripetal force applied by the tracks change by?

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Answer 1 · 2016-09-11T09:19:47

the centripetal force change from 10n to 4n, or decrease at 2,5 times.

Kinetic energy is $\frac{m v^{2}}{2}$ $(mv^2)/2$

The first velocity $v_{1} = \sqrt{15 \cdot \frac{2}{4}} = \sqrt{7, 5}$ $v_1=sqrt(15*2/4)=sqrt(7,5)$

$v_{2} = \sqrt{6 \cdot \frac{2}{4}} = \sqrt{3}$ $v_2=sqrt(6*2/4)=sqrt3$

The centripetal force is $F = m \frac{v^{2}}{r}$ $F=mv^2/r$

$F_{1} = 4 \cdot 7, \frac{5}{3} = 10 n$ $F_1=4*7,5/3=10n$
$F_{2} = 4 \cdot \frac{3}{3} = 4 n$ $F_2=4*3/3=4n$

A model train, with a mass of 4kg4 kg, is moving on a circular track with a radius of 3m3 m. If the train's kinetic energy changes from 15j15 j to 6j6 j, by how much will the centripetal force applied by the tracks change by?