# A model train, with a mass of 16 kg, is moving on a circular track with a radius of 9 m. If the train's kinetic energy changes from 40 j to 9 j, by how much will the centripetal force applied by the tracks change by?

Jul 12, 2017

6.88 N.

#### Explanation:

Here,
In 1st case,

$K E = \frac{1}{2} m {v}^{2}$
$40 \cdot 2 = m {v}^{2}$
$m {v}^{2} / r = \frac{80}{9}$
$F c = \frac{80}{9} N$

In 2nd case,

$m {v}^{2} / r = 2 \cdot \frac{9}{9} = 2$
$F c = 2 N$

$\triangle F c = \frac{80}{9} - 2 = \frac{62}{9} = 6.88 N$

Thank you!!!