Question

A penny is dropped from the top of a building that is 111 m to the ground. What is it’s final speed in m/s

Answer 1

Let the mass of the penny be m.

The height of the building is h = 111 m

Let the velocity be denoted by v.

According to the conservation of energy,

$\begin{gathered} K\text{inetic Energy = Potential energy} \\ \frac{1}{2}mv^2=mgh \end{gathered}$

Here, g = 9.81 m/s^2 is the acceleration due to gravity.

The speed will be

$v=\sqrt[]{2gh}$

Substituting the values, the speed will be

$\begin{gathered} v=\sqrt[]{2\times9.81\times111} \\ =46.67\text{ m/s} \end{gathered}$

Thus, the speed is 46.67 m.