Question

An object thrown vertically upwards, rises to a maximum height of $10\text{m}$. What is the velocity with which it is thrown upwards? (Take $\text{g}=9.8\text{m}{\text{s}}^{-2}$)

• A. 14

Answer 1

The correct option is A 14
Let the upward direction be positive.
Given:
The maximum height reached by the body, $\text{h}=10\text{m}$.
So, displacement is $s=+\text{h}=10\text{m}$
Acceleration due to gravity acts in downward direction. So,
$a=-g=-9.8{\text{m s}}^{-2}$

Let its inital velocity, i.e. the velocity with which it is thrown upwards, be $\text{u}$.
At the highest point, the object changes its direction. So, final velocity, $\text{v}=0$

Using the third equation of motion,
${\text{v}}^2={\text{u}}^2+2\text{as}$
$0^2={\text{u}}^2+2\times (-9.8)\times 10$
$\therefore \text{u}=\sqrt{196}=14\text{m}{\text{s}}^{-1}$