Question

What is the kinetic energy of an object with a mass of `5 kg` that has been in freefall for `4 s`?

Answer 1

About `4000J`

Explanation:

In freefall, I assume acceleration due to gravity, `g` is `10ms^-2`.

`g=(v-u)/t`
We need to find the final velocity `v`. We know that the initial velocity `u=0` and `t=4s`
`g*t=v`
`10ms^-2*4s=40ms^-1`

Kinetic energy is `1/2mv^2=1/2*5kg*(40ms^-2)^2=4000J`