Question

A person throws a ball with speed $10 \,m / s$ at an angle of $30^{\circ}$ with horizontal from the top of $10\, m$ high tower. The distance of ball from the foot of the tower after falling on the ground will be

• A. $7\, m$
• B. $8.6\, m$
• C. $9.6 \,m$
• D. $10\, m$

Answer 1

Answer: (B)

The ball will be at a point $P$ when it is at a height of $10 m$ from the ground. So, we have to find the distance $O P$, which can be calculated directly by considering it as a projectile on a levelled plane $O X$.
Therefore, maximum range, $O P=R=\frac{u^2 \sin 2 \theta}{g}$
$=\frac{10^2 \times \sin \left(2 \times 30^{\circ}\right)}{10}=\frac{10 \sqrt{3}}{2}=5 \sqrt{3}=86 m$