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JEE Main 2023 (1 Feb, Shift 1) · Escape Velocity

Escape Velocity question from JEE Main 2023 (1 Feb, Shift 1)

Q29JEE Main 2023 · 1 FEB · SHIFT 1Easy

Escape Velocity

If earth has a mass nine times and radius twice to that of a planet P. Then ve3x m s−1\frac{v_e}{3}\sqrt{x}\text{ m s}^{-1} will be the minimum velocity required by a rocket to pull out of gravitational force of PP, where vev_e is escape velocity on earth. The value of xx is

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Answer: (c)

  1. v∝MRv \propto \sqrt{\frac{M}{R}}; planet P has M9\frac{M}{9} and R2\frac{R}{2}
  2. vP=ve1/91/2=ve29=ve32v_P = v_e\sqrt{\frac{1/9}{1/2}} = v_e\sqrt{\frac{2}{9}} = \frac{v_e}{3}\sqrt{2}
  3. So x=2x = 2, answer (c).
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