Physics Two Dimensional Motion Question 159

Question: The equation of trajectory of projectile is given by$ y=\frac{x}{\sqrt{3}}-\frac{\text{g}{{x^{2}}}{20} $ , where x and y are in meter. The maximum range of the projectile is

Options:

A) $ \frac{8}{3}\text{ m} $ B)$ \frac{4}{3}\text{ m} $ C) $ \frac{3}{4}\text{ m} $ D)$ \frac{3}{8}\text{ m} $

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Answer:

Correct Answer: B

Solution:

[b] Comparing the given equation with the equation of trajectory of a projectile, $ y=x,,\tan \theta -\frac{\text{g}{{x^{2}}}{2{{u^{2}}{{\cos }^{2}}\theta }, $ we get, $ \text{tan}\theta ,\text{=},,\frac{1}{\sqrt{3}}\Rightarrow \theta =30{}^\circ $ and $ 2{{u^{2}}{{\cos }^{2}}\theta =20\Rightarrow {{u^{2}}=\frac{20}{2{{\cos }^{2}}\theta }=\frac{40}{3} $ Now, $ {{\text{R}} _{\max }}=\frac{{{u _{2}}}{\text{g}}=\frac{40}{3\times 10}=\frac{4}{3}\text{m} $