# A ball is falling from the top of a cliff of height h with an initial speed V. Another ball …

Q: A ball is falling from the top of a cliff of height h with an initial speed v . Another ball is simultaneously projected vertically up with the same speed. When do they meet ?

[ Ans: h/2v ]

Sol: For downward motion

$\displaystyle h_1 = v t + \frac{1}{2}g t^2$ …(i)

For upward motion

$\displaystyle h_2 = v t – \frac{1}{2}g t^2$ …(ii)

Adding (i) & (ii)

$\displaystyle h_1 + h_2 = v t + vt$

$\displaystyle h = 2 v t$

$\displaystyle t = \frac{h}{2 v}$