Question

. A rock is dropped from a height of 4 m. How fast is it going when it hits the ground? The rock has a mass of 2 kg. (Hint: MEi = MEf)

Answer 1

8.85 m/s

Step-by-step explanation:

Answer 2

Hello!

When the rock is dropped, it only contains Gravitational Potential Energy, and when it hits the ground, it contains Kinetic Energy.

So:

PE = KE

`\large\boxed{mgh = (1)/(2)mv^2}`

We can rearrange to solve for velocity. Cancel out mass and solve.

`gh = (1)/(2)v^2\\\\2gh = v^2\\\\v = √(2gh)`

Plug in the givens:

`v = √(2(9.8)(4)) = \boxed{8.85 (m)/(s)}`