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Q & A: Escape Velocity

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Most recent answer: 10/22/2007
Q:
What is the speed required for an object (like a rocket) to overcome the force of earth’s gravity ? Is this called "exit velocity ?"
- Steve
Chilliwack, BC, Canada
A:
Steve -

You are right that this is sometimes called "exit velocity". It is also sometimes called "escape velocity". The escape velocity from the Earth's surface is about 11.2 km/sec (ignoring air resistance). This is the speed with which you would have to launch something from the surface of the earth if you wanted it to completely escape from the earths gravitational pull. Since most rockets fire their engines for quite a long time (until the rocket is already rather far from the earths surface), there is actually no need for the kind of rockets we are used to ever go this fast.

-Tamara & Tim

(published on 10/22/2007)

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