An object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.

F = ma. The vector sum of the forces F on an object is equal to the mass m (constant) of that object multiplied by the acceleration a of the object: F = ma.

For every action there is an equal and opposite re-action.

Particle attracts all others using a force directly proportional to the product of their masses & inversely proportional to the square of the distance between their centers.

All planets move in elliptical ___, with the sun at one focus.

A line that connects a planet to the sun sweeps out equal ___ in equal times.

The square of the ___ of any planet is proportional to the cube of the semi-major axis of its orbit.

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