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3-2.Motion in Plane
hard
A projectile is launched at an angle ' $\alpha$ ' with the horizontal with a velocity $20 \; ms ^{-1}$. After $10 s$, its inclination with horizontal is ' $\beta$ '. The value of $\tan \beta$ will be : $\left( g =10 \; ms ^{-2}\right)$
A
$\tan \alpha+5 \sec \alpha$
B
$\tan \alpha-5 \sec \alpha$
C
$2 \tan \alpha-5 \sec \alpha$
D
$2 \tan \alpha+5 \sec \alpha$
(JEE MAIN-2022)
Solution

$v_{x}=u_{x}=20 \cos \alpha$
$v_{y}=20 \sin \alpha-10 \times 10$
$\tan \beta=\frac{v_{y}}{v_{x}}=\frac{20 \sin \alpha-100}{20 \cos \alpha}$
$=\tan \alpha-5 \sec \alpha$
Standard 11
Physics