# If an object with a mass of 15 kg  changes speed from 25m/s to 14 m/s, by how much does its kinetic energy change?

##### 1 Answer
Feb 13, 2016

$\Delta {E}_{k} = - 3217 , 5 J$

#### Explanation:

$\Delta {E}_{k} = \frac{1}{2} \cdot m \left({v}_{f}^{2} - {v}_{i}^{2}\right)$
$\Delta {E}_{k} = \frac{1}{2} \cdot 15 \left({14}^{2} - {25}^{2}\right)$
$\Delta {E}_{k} = \frac{1}{2} \cdot 15 \left(196 - 625\right)$
$\Delta {E}_{k} = - \frac{1}{2} \cdot 15 \cdot 429$
$\Delta {E}_{k} = - 3217 , 5 J$