JOHANNAS KEPLER -

Developed 3 laws that all planets follow while in orbit!

WARM - UP

Warm-Up Question Answer…

Kepler’s First Law

The orbit of the planets are ellipses, with the sun at

one focus of the ellipse.

Draw the sun and Earth and indicate the direction

of orbit on your paper.

Ellipses and Eccentricity

The amount of flattening of the ellipse is termed the

eccentricity.

Circle = 0

Straight Line = 1

Ellipses

The sun is not at the center of the ellipse.

There is nothing at the other focus.

Astronomical Distances

An Astronomical Unit (AU) is the average distance

between Earth and the Sun.

Used when measuring distances to other solar system

objects.

A Light year is the distance it takes light to travel in

1 year.

Used to measure distances to other stars and galaxies.

Kepler’s Second Law

The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse.

As the planet approaches the sun… Orbital Speed will Increase

Gravitational force will Increases

As the planet travels away from the sun… Orbital Speed will decrease

Gravitational force will decrease

Kepler’s Third Law

The closer the object is to the Sun the faster its

period of revolution.

Example:

Earth & Mars Orbit

Get your computer – Log on to our website (orbital motion page)

Three links are at the bottom for Kepler’s 1st, 2nd, and 3rd Law