# What is the kinetic energy of an object with a mass of 3  kg that has been in freefall for 9  s?

First step is to calculate the velocity, $v = u + a t = 0 + 9.8 \cdot 9 = 88.2$ $m {s}^{-} 1$.
Second step is to use this to calculate the kinetic energy, ${E}_{k} = \frac{1}{2} m {v}^{2} = \frac{1}{2} \cdot 3 \cdot {88.2}^{2} = 11669$ $J = 11.7$ $k J$.
The initial velocity, $u$ can be assumed to be $0$ $m {s}^{-} 1$ if we are not told otherwise, and the acceleration is just the acceleration due to gravity, $9.8$ $m {s}^{-} 2$.