If the gravitational attraction between the Earth and an orbiting satellite were to vanish instantaneously, what would the satellite do?

move off along the tangent to its orbit at its current speed
keep moving in the same orbit at the same speed
stay at rest where it was
fall straight towards the Earth

Correct answer: move off along the tangent to its orbit at its current speed

Solution

Removing gravity leaves no centripetal force. By Newton's first law the satellite continues in a straight line at constant speed, which is along the tangent to the orbit at the moment gravity disappears.

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