JEE MAIN - Physics (2024 - 1st February Morning Shift - No. 18)
If this particle is projected with the same speed at an angle $\theta$ to the horizontal, the maximum height attained by it is equal to $4 R$. The angle of projection $\theta$ is then given by :
Explanation
To solve for the angle of projection $\theta$, we will first establish the relationship between the variables given and then derive the formula using kinematics.
The time $T$ for one revolution at speed $v$ in a circle of radius $R$ is related to the circumference of the circle by the formula:
$$ v = \frac{2\pi R}{T} $$
When the particle is projected with the same speed $v$ at an angle $\theta$ to the horizontal, its vertical component of velocity is given by $v_y=v\sin\theta$.
The maximum height $H$ reached by the projectile can be found from the kinematic equation:
$$ H = \frac{v_y^2}{2g} = \frac{(v\sin\theta)^2}{2g} $$
We are given that the maximum height attained $H$ is equal to $4R$, so:
$$ 4R = \frac{(v\sin\theta)^2}{2g} $$
Substitute $v$ from the first equation into the second one:
$$ 4R = \frac{((\frac{2\pi R}{T})\sin\theta)^2}{2g} $$
$$ 4R = \frac{(2\pi R\sin\theta)^2}{2gT^2} $$
$$ 4R = \frac{4\pi^2 R^2 \sin^2\theta}{2gT^2} $$
$$ 2gT^2 = \pi^2 R \sin^2\theta $$
Now solve for $\sin\theta$:
$$ \sin\theta =\left[\frac{2gT^2}{\pi^2 R}\right]^{1/2} $$
Finally, to solve for $\theta$, take the inverse sine of both sides:
$$ \theta = \sin^{-1}\left(\left[\frac{2gT^2}{\pi^2 R}\right]^{1/2}\right) $$
Therefore, the correct answer is:
Option A
$$ \sin^{-1}\left[\frac{2gT^2}{\pi^2 R}\right]^{1/2} $$
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