Other Laws of Motion

Newton’s three laws of motion are the most well known, but there are other such laws. Newton’s work on forces, motion, and gravity built on earlier work by German mathematician Johannes Kepler (1571-1630). Kepler studied the way that the planets move. Using observations of the planets made by Danish astronomer Tycho Brahe (1546-1601), Kepler produced three laws of motion for planets.

Kepler’s first law says the shape of a planet’s orbit is a squashed circle, or ellipse. The second law says a line between a star and a planet sweeps out equal areas in equal periods of time. A planet, therefore, travels through space faster when it is closer to a star and more slowly when it is farther away from the star. Kepler’s third law describes the link between the time it takes a planet to go around a star and the length of its orbit.

Newton’s laws of motion and gravi­tation provided a scientific explanation for Kepler’s laws. Kepler’s laws describe the motion of planets, but they apply equally to the motion of modern-day satellites and manned spacecraft travel­ing around planets and moons.

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SEE ALSO:

• Force • Gravity • Lift and Drag

• Newton, Isaac • Thrust • Weight

and Mass

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