Q. A particle is thrown with a speed $u$ at an angle $\theta$ with the horizontal. When the particle makes an angle $\alpha$ with the horizontal, its speed becomes $v$, whose values is
A) $u\ cos\ \theta$
B) $u\ cos\ \theta\ cos\ \alpha$
C) $u\ cos\ \theta\ sec\ \alpha$
D) $u\ sec\ \theta\ cos\ \alpha$
Explanation
(c) In projectile motion given angular projection, the horizontal component velocity remains unchanged. Hence
$v\cos{\alpha = u\ cos\ \theta}\ $or $v = u\cos{\theta\sec\alpha}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.