A stone is dropped from the top of a tower of height `h`. Aftre `1 s` another stone is droppped from the balcony `20 m` below the top. Both reach the bottom simultaneously. What is the value of `h` ? Take `g=10 ms^(-2)`.

Options

A. `31 5m`
B. ` 312.5 m`
C. ` 3125 m`
D. ` 25,31`

Answer

C

Explanation

`h=(1)/(2) g t^(2)` and `h-20=(1)/(2)g(t-1)^(2)`
Solving them, we get `t=2.5 s` and `h=31.25 m`.