# If an object with a mass of 2 kg  changes speed from 2m/s to  7m/s, by how much does its kinetic energy change?

Feb 17, 2016

$\Delta {E}_{k} = 45 J$

#### Explanation:

${E}_{k f} \text{ :final kinetic energy}$
${E}_{k i} : \text{ initial kinetic energy}$
$\Delta {E}_{k} = {E}_{k f} - {E}_{k i}$
$\Delta {E}_{k} = \frac{1}{2} \cdot m \cdot \left({v}_{f}^{2} - {v}_{i}^{2}\right)$
$\Delta {E}_{k} = \frac{1}{2} \cdot 2 \left({7}^{2} - {2}^{2}\right)$
$\Delta {E}_{k} = 49 - 4$
$\Delta {E}_{k} = 45 J$