# What is the kinetic energy of an object with a mass of 3 kg that has been in freefall for 6 s?

Jan 31, 2016

I found $5 , 186 J$

#### Explanation:

the object will fall from a height given as:
${y}_{f} - {y}_{i} = {v}_{i} t + \frac{1}{2} a {t}^{2}$
where:
${y}_{f} = 0$ the ground;
${y}_{i} = h$ is the height from which the object is falling;
${v}_{i} = 0$ the initial velocity;
$t$ is the time;
$a$ is the acceleration of gravity.
We then get:
$- {y}_{i} = - \frac{1}{2} \cdot 9.8 \cdot \left({6}^{2}\right)$
so ${y}_{i} = 176.4 m$
When the object falls potential energy $U = m g h$ is converted into Kinetic Energy $K$.
so::
$U = 3 \cdot 9.8 \cdot 176.4 = 5 , 186 J$ that will be our kinetic energy.