Question

A stone is thrown upwards with a speed v from the top of a tower. It reaches the ground with a velocity 3v. What is the height of the tower?

Answer 1

From equation of motion, 

v’ = u + at ……. (1)

 h = ut + \(\frac{1}{2}\)at² 

here, v’ = av; u = v; a = +g

Using equ. (1) 

3v = v + gt ⇒ 3v – v = gt

t = \(\frac{2u}{g}\)

Substitute ‘t’ value in equ. (2)