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JEE Main 2022 (24 Jun, Shift 1) · Time of Flight, Maximum Height & Range

Time of Flight, Maximum Height & Range question from JEE Main 2022 (24 Jun, Shift 1)

Q23JEE Main 2022 · 24 JUN · SHIFT 1Medium

Time of Flight, Maximum Height & Range

A projectile is projected with velocity of 25 m/s at an angle θ\theta with the horizontal. After t seconds its inclination with horizontal becomes zero. If R represents horizontal range of the projectile, the value of θ\theta will be:

[use g = 10 m/s2]

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Answer: (d)

  1. Inclination zero means the top: t=usin⁡θg⇒usin⁡θ=10tt = \frac{u\sin\theta}{g} \Rightarrow u\sin\theta = 10t
  2. R=2(usin⁡θ)(ucos⁡θ)g=2t ucos⁡θ⇒ucos⁡θ=R2tR = \frac{2(u\sin\theta)(u\cos\theta)}{g} = 2t\,u\cos\theta \Rightarrow u\cos\theta = \frac{R}{2t}
  3. tan⁡θ=10tR/2t=20t2R⇒cot⁡θ=R20t2\tan\theta = \frac{10t}{R/2t} = \frac{20t^2}{R} \Rightarrow \cot\theta = \frac{R}{20t^2}
  4. So the answer is (d) cot⁡−1(R20t2)\cot^{-1}\left(\frac{R}{20t^2}\right).
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