Question

find g at a height double of earth radius

Answer 1

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Since the radius of the Earth is 6378 km, that is our initial "r", if we are standing on the ground. That's our answer. At an altitude of 2642 km (approx. 1641 miles) above the Earth's surface, the gravitational acceleration will be 4.89m/s^2, which is half of 9.78 m/s^2 .

In fact, at an altitude of 400 kilometres (250 mi), equivalent to a typical orbit of the Space Shuttle, gravity is still nearly 90% as strong as at the Earth's surface. Weightlessness actually occurs because orbiting objects are in free-fall.

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