Question

Question 5
A stone is thrown in a vertically upward direction with a velocity of $5m{s}^{-1}$. If the acceleration of the stone during its motion is $10m{s}^{-2}$ in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

Answer 1

Given initial velocity of the stone, $u=5m{s}^{-1}$, acceleration, $a=-10m{s}^{-2}$ (negative as it is in vertically downward direction)
At highest point, final velocity, $v=0$
From third equation of motion, $v^2-u^2=2as$
$0^2-5^2=2\times -10\times s$
Therefore, height attained by the stone, $s=\frac{-25}{-20}=1.25m$
Also we know that final velocity, v = u + at
or, time, $t=\frac{v-u}{a}$
$t=\frac{0-5}{-10}$
$=0.5s$