Question

A body is projected horizontally from the top of a tower with an initial velocity of $18{\text{ms}}^{-1}$. It hits the ground at an angle of ${45}^{\circ }$ with horizontal. What is the vertical component of velocity when the body strikes the ground?

• A. $9\text{m/s}$
• B. $9\sqrt{2}\text{m/s}$
• C. $18\text{m/s}$
• D. $18\sqrt{2}\text{m/s}$

Answer 1

The correct option is C $18\text{m/s}$

Let $v$ be the velocity with which body strikes the ground.
Horizontal component of velocity doesn’t change during the motion.
$\therefore v\cos {45}^{\circ }=u=18\text{m/s}\Rightarrow v=18\sqrt{2}\text{m/s}$

Vertical component when it strikes the ground $=v\sin {45}^{\circ }=18\sqrt{2}\times \frac{1}{\sqrt{2}}=18\text{m/s}$