I was thinking about the orbital speed of a satellite around the earth which works out to 7900 meters per second according to my "Physics the Easy Way" book. They use the formula of V = square root (gr) where g is 9.8 meters per second and r is the radius of the earth or 6.4 million meters. But considering conservation of energy, the potential energy of a satellite with a mass of 1 Kg at 6.4 million meters height would be (mgh) or 62.72 million joules relative to the center of the earth. So, if it falls the distance of the radius of the earth, the kenetic energy will be 62.72E6 = 1/2 MV^2 and V will be 11,200 meters per second. Wiki has an interesting formula of v = square root of gm/r which makes no sense. So, why is the orbital speed around the earth 7.9 Km/s and not 11.2 Km/s ?
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