Question

An object of unknown mass is dropped from rest from a height of 100 m above ground level. How long does it take the object to reach the ground?

Answer 1

Given data

*The given height is h = 100 m

*The value of the acceleration due to gravity is g = 9.8 m/s^2

*The initial speed of an object is u = 0 m/s

The formula for the time taken by the object to reach the ground is given by the equation of motion as

$h=ut+\frac{1}{2}gt^2$

Substitute the known values in the above expression as

$\begin{gathered} 100=(0)t+\frac{1}{2}(9.8)t^2 \\ t^2=20.40 \\ t=\sqrt[]{20.40} \\ =4.52\text{ s} \end{gathered}$

Hence, the time taken by the object to reach the ground is t = 4.52 s