# What is the kinetic energy of an object with a mass of 3 kg that has been in freefall for 7 s?

May 19, 2016

${E}_{k} = 7073.35 \text{ } J$

#### Explanation:

$\text{first; let's find velocity of object for t=7}$

$v = - g \cdot t$
$v = - 9 \cdot 81 \cdot 7$
$v = - 68.67 \frac{m}{s}$

$\text{The Kinetic Energy of an object is calculated by:} {E}_{k} = \frac{1}{2} \cdot m \cdot {v}^{2}$

$m = 3 k g$

${E}_{k} = \frac{1}{2} \cdot 3 \cdot {\left(- 68.67\right)}^{2}$

${E}_{k} = 7073.35 \text{ } J$