A stone is thrown vertically upwards with a speed of 20 m/s. How high will it go before it begins to fall? $(g=9.8\ m/s^2)$

As given, the initial speed of the stone $u=20\ m/s$

Gravitational acceleration $g=8\ m/s^2$ 

Final speed $v=0$   [At the maximum height velocity of the stone will be zero]

Let the maximum height will be $h$.

On using the equation of the motion, $v^2=u^2+2gh$

$0=20^2+2\times(-8)\times h$     [As stone is going upward, $g$ will be negative]

Or $0=400-16h$

Or $16h=400$

Or $h=\frac{400}{16}$

Or $h=25\  m$

Therefore, the stone will go $25\ m$ high before it begins to fall.

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Updated on: 10-Oct-2022

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