# A model train, with a mass of 32 kg, is moving on a circular track with a radius of 3 m. If the train's kinetic energy changes from 18 j to 21 j, by how much will the centripetal force applied by the tracks change by?

##### 1 Answer
Mar 4, 2018

$2 N$

#### Explanation:

suppose,initial velocity was $u$ and then final velocity became $v$,so for a mass of $m$,we can say,its change in kinetic energy will be, $\frac{1}{2} m \left({v}^{2} - {u}^{2}\right) = 21 - 18 = 3$

so, $m \left({v}^{2} - {u}^{2}\right) = 6. \ldots \ldots \ldots \ldots \ldots \ldots \ldots 1$

Now,change in centripetal force will be $\frac{m}{r} \left({v}^{2} - {u}^{2}\right) = \frac{6}{r} = \frac{6}{3} = 2 N$ (from $1$ and given, $r = 3 m$)