Answer :
Given,
The mass of the balls, m₁=5 kg and m₂=20 kg
The height of the cliff, h=80 m
As the balls are dropped and not thrown, their initial velocity is u=0 m/s
The acceleration due to gravity, g=10 m/s/s
The time it takes for an object to fall to the ground from a certain height does not depend on its mass. It only depends on the height from which it is dropped, the initial velocity with which it is thrown and the acceleration due to gravity.
As both balls are dropped from the same height, they both take the same amount of time to reach the ground.
From the equation of motion,
[tex]h=ut+\frac{1}{2}gt^2[/tex]Where t is the time it takes to the balls to reach the ground.
On substituting the known values,
[tex]\begin{gathered} 80=0+\frac{_{}1}{2}\times10\times t^2 \\ \Rightarrow t=\sqrt[]{\frac{2\times80}{10}} \\ =4\text{ s} \end{gathered}[/tex]Thus both balls take 4 s to hit the ground.
