# If an object with a mass of  3kg  changes speed from 5m/s to  1m/s, by how much does its kinetic energy change?

Apr 4, 2016

$\Delta {E}_{k} = - 36 J$

#### Explanation:

${v}_{f} = 1 \frac{m}{s}$
${v}_{i} = 5 \frac{m}{s}$
$m = 3 k g$

$\Delta {E}_{k} = \frac{1}{2} \cdot m \left({v}_{f}^{2} - {v}_{i}^{2}\right)$

$\Delta {E}_{k} = \frac{1}{2} \cdot 3 \cdot \left({1}^{2} - {5}^{2}\right)$

$\Delta {E}_{k} = \frac{3}{2} \left(1 - 25\right)$

$\Delta {E}_{k} = - \frac{3}{\cancel{2}} \cdot {\cancel{24}}^{12}$

$\Delta {E}_{k} = - 3 \cdot 12$

$\Delta {E}_{k} = - 36 J$