# What is the kinetic energy of an object with a mass of 3 kg that has been in freefall for 28 s?

Dec 21, 2015

$112.9 \text{kJ}$

#### Explanation:

We need to get the velocity of the object after it has fallen under gravity for 28s.

We can use $v = u + a t$

This becomes:

$v = 0 + 9.8 \times 28$

$\therefore v = 274.4 \text{m/s}$

The kinetic energy is given by:

KE = $\frac{1}{2} m {v}^{2}$

$\therefore \text{KE"=1/2xx3xx274.4^(2)=112,943"J}$

$= 112.9 \text{kJ}$