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JEE Main 2023 (11 Apr, Shift 2) · Escape Velocity

Escape Velocity question from JEE Main 2023 (11 Apr, Shift 2)

Q37JEE Main 2023 · 11 APR · SHIFT 2Medium

Escape Velocity

A space ship of mass 2×104 kg2 \times 10^{4}\text{ kg} is launched into a circular orbit close to the earth surface. The additional velocity to be imparted to the space ship in the orbit to overcome the gravitational pull will be (if g=10 m/s2g = 10\text{ m/s}^{2} and radius of earth =6400 km= 6400\text{ km} ):

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Answer: (d)

  1. Orbit close to the surface: vo=gRv_o = \sqrt{gR}; escape speed from there: ve=2gR=2 vov_e = \sqrt{2gR} = \sqrt{2}\,v_o.
  2. vo=10×6.4×106=8×103 m/s=8 km/sv_o = \sqrt{10 \times 6.4 \times 10^{6}} = 8 \times 10^{3}\text{ m/s} = 8\text{ km/s}
  3. Extra speed =ve−vo=8(2−1) km/s= v_e - v_o = 8(\sqrt{2}-1)\text{ km/s} (mass is not needed).
  4. So the answer is (d) 8(2−1) km/s8(\sqrt{2}-1)\text{ km/s}.
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