Question

A stone thrown upward with a speed u from the top of the tower reaches the ground with a velocity 3u. The height of the tower is

• A. $3u^{2}/g$
• B. $4u^{2}/g$
• C. $6u^{2}/g$
• D. $9u^{2}/g$

Answer 1

Answer: (B)

$4u^{2}/g$

Answer 2

For vertical downward motion we will consider initial

velocity = – u.

By applying $v^{2} = u^{2} + 2gh$, $(3u)^{2} = ( - u)^{2} + 2gh$

⇒ $h = \frac{4u^{2}}{g}$.