Q. A stone is projected from the ground with velocity $50\ ms^{- 1}$ and angle of $30{^\circ}$. It crosses a wall after 3 s. How far beyond the wall the stone will strike the ground?
A) 80.5 m
B) 85.6 m
C) 86.6 m
D) 75.2 m
Explanation
(c) $T = \frac{2 \times 50 \times \frac{1}{2}}{10} = 5\ s$
Horizontal distance travelled in last 2 s
$= 50 \times \cos{30{^\circ}} \times 2\ m$
$= 100 \times \frac{2}{\sqrt{3}}m = 50\sqrt{3}m = 86.6\ m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.