Question

A stone thrown upward with a speed u from the top
of a tower reaches the ground with a velocity 4u. The
height of the tower is​

Answer 1

$\huge\mathcal\green\boxed{\boxed{Answer:-}}$

Given:-

The stone is thrown upward with velocity 'u'.

and, the stone comes back with a velocity '4u'.

Explanation

$v = 4u$

$u = u$

$a = g$

$s = h$

Now from third kinematic equation it becomes,

${v}^{2} - {u}^{2} = 2as$

$( {4u})^{2} - ( {u})^{2} = 2gh$

${16u}^{2} - {u}^{2} = 2gh$

${15u}^{2} = 2gh$

$h = \frac{ {15u}^{2} }{2g}$

$\boxed{\boxed{h = \frac{ {15u}^{2} }{2g}}}$

so,the height of tower is 15u^2/2g