Q. The kinetic energy of a projectile at the highest point is half of the initial kinetic energy. What is the angle of projection with the horizontal?
A) $30{^\circ}$
B) $45{^\circ}$
C) $60{^\circ}$
D) $90{^\circ}$
Explanation
(b) $(KE)_{H} = \frac{1}{2}(KE)_{i}$
$\frac{1}{2}mv^{2}\cos^{2}\theta = \frac{1}{2}\left( \frac{1}{2}mv^{2} \right) = \frac{1}{4}mv^{2}$
or $\cos^{2}\theta = \frac{1}{2}\ \ or\ \ \cos\theta = \frac{1}{\sqrt{2}}\ \ or\ \ \theta = 45{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.