Question

A ball falls from ht. H . After 1 sec , another ball falls freely from a point 20 m below the pt. From where 1st ball fell. both of them reach ground at same time . WhAt is value of h?

Answer 1

Dear Student,

time taken by first ball to touch ground.

using second eqn of motion .

$$\begin{gathered} h=\frac{g{t}^2}{2} \\ forsecondball \\ h-20=\frac{10(t-1{)}^2}{2}putvalueofhandsolvefort \\ 5t^2-20=5(t-1{)}^2 \\ t=2.5sec \\ nowwegotthetimeforfirstballthatis2.5sec \\ h=\frac{g\times 2.5^2}{2}=6.25\times 5=31.25m \\ Regards \end{gathered}$$