A satellite in a circular orbit around the Earth is held in orbit by
Correct answer: C. the gravitational pull of the Earth acting as the centripetal force
- A. the vacuum of space
- B. its own centrifugal force
- C. the gravitational pull of the Earth acting as the centripetal force
- D. the thrust of its engines
Explanation
Gravity supplies exactly the inward force needed to bend the satellite's straight line motion into a circle, so no engine is required once the orbit is established. Setting the gravitational force equal to mv squared over r gives the orbital speed, which depends on the radius but not on the satellite's mass. Astronauts feel weightless because they and the craft are falling towards the Earth together, not because gravity is absent.
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About Angular and Linear Quantities
Rotational motion relates angular displacement, angular velocity and angular acceleration to linear displacement, tangential velocity and tangential acceleration through the radius. Questions use radians, v equals r omega and tangential acceleration, while distinguishing tangential velocity from centripetal acceleration and angular quantities from their linear counterparts.
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