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Remember that the "critical" velocity is the velocity that a near-earth satellite needs to stay in orbit. That velocity, as you can find in any physics textbook, is critical v = sqrt( GM / R ) where G is the gravitational constant, M is the mass of the earth, and R is the radius of the satellite's orbit, assumed to be close enough to the surface that R is almost the radius of the earth. For the escape velocity, that velocity needed for an object to escape from the surface of the earth, the formula is escape v = sqrt( 2GM / R ) and so the ratio escape v / critical v = sqrt( 2 ) which is approximately 1.4

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