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## Worked example 12.2: Acceleration of a rocket

Question: A rocket is located a distance 3.5 times the radius of the Earth above the Earth's surface. What is the rocket's free-fall acceleration?

Answer: Let be the Earth's radius. The distance of the rocket from the centre of the Earth is . We know that the free-fall acceleration of the rocket when its distance from the Earth's centre is (i.e., when it is at the Earth's surface) is . Moreover, we know that gravity is an inverse-square law (i.e., ). Hence, the rocket's acceleration is

Richard Fitzpatrick 2006-02-02