Planetary Motion Objectives Explain the difference between rotation

Planetary Motion

Objectives: • Explain the difference between rotation and revolution. • Describe three laws of planetary motion. • Describe how distance and mass affect gravitational attraction.

Standard and Benchmark • 8. 4. 3 Know that gravity holds the planets in orbit around the Sun and the moons in orbit around the planets

Warm-up Activity/Pre. Assessment • Class Brainstorm/Cluster • As a class we will Brainstorm Ideas that come to mind when we hear Planetary Motion. • Think of what holds the planet in place. • Why doesn’t it fly off to space? , etc. • Wordle. net

Vocabulary • Rotation: the spin of a body on its axis. • Orbit: the path of a body follows as it travels around another body in space. • Revolution: the motion of a body that travels around another body in space; once complete trip along an orbit.

A Revolutionary in Astronomy • Kepler’s First Law of Motion The planets move around the sun in an ellipse. • Kepler’s Second Law of Motion the planets seemed to move faster when they are close to the sun and slower when they are farther away. • Kepler’s Third Law of Motion Planets further from the sun, such as Saturn, take longer to orbit the sun.

Earth’s Rotation and Revolution

Newton to the Rescue! • The Law of Universal Gravitation Newton’s law of universal gravitation states that the force of gravity depends on the product of the masses of the objects divided by the square of the distance between the objects. • Orbits Falling Down and Around Gravity keeps the moon from flying off in a straight path. This principle holds true for all bodies in orbit, including the Earth and other planets in our solar system.

Gravity and Motion of the Moon In this figure, Gravity causes the moon to fall toward the Earth and changes a straight-line path into a curved orbit.

Questions?