Q. A project is projected with a velocity of $20\ m/s$ making an angle of $45{^\circ}$ with horizontal. The equation for the trajectory is $h = Ax - Bx^{2}$ where $h$ is height, $x$ is horizontal distance, $A$ and $B$ are constants. The ratio $A\ :B$ is $(g = 10\ ms^{- 2})$

A) $1\ :5$
B) $5\ :1$
C) $1\ :40$
D) $40\ :1$
Explanation

(d) Standard equation of projectile motion
$y = x\tan\theta - \frac{gx^{2}}{2u^{2}\cos^{2}\theta}$
Comparing with given equation
$A = \tan\theta$ and $B = \frac{g}{2u^{2}\cos^{2}\theta}$
So $\frac{A}{B} = \frac{\tan\theta \times 2u^{2}\cos^{2}\theta}{g} = 40$
[As $\theta = 45{^\circ},\ u = 20\ m/s,\ g = 10m/s^{2}$]

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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