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A black hole is a body from whose surface nothing may ever escape. What is the condition for a uniform spherical mass M to be a black hole? What should be radius of earth if it has to be a black hole? |
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Answer» For a body to be a black hole, even light should not escape. So limiting escape velocity is 3 × 108 ms-1 So, for body of Mass M, condition is, \(\sqrt \frac {2GM}{R}\) ≥ 3 × 108 ms-1 For Earth, M = 6 × 1024 kg \(\frac {2 \times 6.67 \times 10^{-11} \times 6 \times 10^{24}}{R}\) = (3 × 108)2 R = 9 × 10-2 m R = 9 cm. |
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