Q. A particle is projected from horizontal making an angle $60{^\circ}$ with initial velocity $40ms^{- 1}$. The time taken by the particle to make angel $45{^\circ}$ from horizontal, is

A) 15 s
B) 2.0 s
C) 20 s
D) 1.5 s
Explanation

(d) At $45{^\circ},v_{x} = v_{y}$
or $u_{x} = u_{y} - gt$
$\therefore\ \ t = \frac{u_{y} - u_{x}}{g}$
$= \frac{40(\sin{60{^\circ}} - \sin{30{^\circ}})}{9.8} = 1.5\ s$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.