Question

A man drops a 10 kg rock from the top of a 5m ladder.what is its speed just before it hits the ground?what is its kinetic energy when it just reaches the ground?

Answer 1

Mass of rock =10 Kg

Length of ladder (Height) =5m

Acceleration due to gravity = 9.8 m/s²

Initial velocity = 0 m/s

Using Equation of motion
v²-u²=2as

v²=2 x 9.8 x 5

v²=98

$\Rightarrow$ v = 9.899
kinetic energy when it just reaches the ground =
=$$\begin{gathered} \frac{1}{2}m{v}^2 \\ \frac{1}{2}\left(10\right)(9.899{)}^2 \\ =490kg{m}^2/s^2 \end{gathered}$$