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Question:

The escape velocity from the earth is about 11 kms. The escape velocity from a planet having twice the radius and the same mean density as the earth is?

5.5kms

22kms

11kms

15.5kms

Solution:

The correct option is B (22kms)
The value of escape velocity from a planet = √GMR = √(Gρ(4/3)πR³)/R ∝ √ρR²
Hence vp/ve = √(ρpRp²/ρeRe²) = 2Re/Re = 2 => vp = 22km/s