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Circular Orbits
The shuttle is in a nearly circular orbit around the Earth. To stay in this orbit around the Earth, the shuttle must be given forward speed initially so that it does not fall to the ground from the force of gravity. If there was no gravity, the shuttle's forward speed would cause it to fly off into space. Gravity keeps the shuttle flying around the Earth by constantly pulling it towards the center of the Earth.
[[image]] Gravity
Forward Motion
of the Shuttle

Free-Fall Motion
If you were in a circular orbit around the Earth, you would feel like you were falling. This condition is called free-fall. The astronauts and everything inside of the shuttle are falling together at the same rate, no matter how big or heavy they are. In free-fall you do not feel the force of gravity even though gravity is present. The shuttle never escapes the Earth's gravity. In fact, gravity is what keeps the shuttle falling around the Earth!

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Transcription Notes:
grabity and forward motion of the shuttle are labels for the image.