Question

Two stones are dropped from the top of a tower at half a second apart. The time after dropping the first stone at which the distance between the two stones is 20 m is $(g=10m{s}^{-2})$

• A. 4 s
• B. 3.75 s
• C. 4.25 s
• D. 0.53 s

Answer 1

The correct option is C 4.25 s

If the first stone travels for t sec then the second stone travels for (t -0.5) sec.

$h_1=5t^2$ ___(1) $g=10$

$h_2=5{\left[t-\frac{1}{2}\right]}^2$

$20=h_2=5{\left[t-\frac{1}{2}\right]}^2$____(2)

on solving we get (1) and (2) we get

$t=4.25\sec .$