Kepler's Laws

Kepler's Laws

Ms. Dang

How do Kepler’s laws describe Earth’s orbit?

Beginnings

Johannes Kepler, working with data painstakingly collected by Tycho Brahe (from 1576-1601) without the aid of a telescope, developed three laws which described the motion of the planets across the sky. 

Kepler’s First Law

Law of Orbits: All planets move in elliptical orbits, with the sun at 1 focus.

An ellipse is an oval shape centered on 2 points instead of 1 point.

The orbital period of a planet is how long it takes for it to travel a complete orbit around the Sun… a year!

Perihelion

Aphelion

Kepler’s Second Law

Law of Areas: A line that connects a planet to the Sun sweeps out equal (=) areas in equal (=) times.

Earth sweeps out a longer path when it is closer to the Sun.

Earth moves fastest when it is closest to the Sun

Kepler’s Third Law

Law of Periods: The square of the orbital period of any planet is proportional to the cube of the semi major axis of its orbit. 

T² = a³ If you know the distance of a planet to the Sun, you would be able to figure out its… orbital period. Basically… The closer a planet is to the Sun, the shorter its orbital period is. 

Multiple Choice

Planets orbit the Sun in a shape called a(n)

• circle

• ellipse

• focus

• perihelion

Multiple Choice

An ellipse is drawn around two points called

• aphelion
• perihelion
• foci
• axis

Multiple Choice

When a planet orbits the Sun, one of the foci of the elliptical orbit is 

• the axis
• the perihelion
• the center
• the Sun

Multiple Choice

The place where a planet is closest to the Sun as it orbits the Sun is called the

• perihelion
• aphelion

Multiple Choice

The place where a planet is farthest away from the Sun in its orbit around the Sun is called the

• aphelion
• perihelion

Multiple Choice

Where is the planet moving faster

• Position A to B
• Position B to C
• Position H to I
• Position I to J

Multiple Choice

What is true about the area between points A, B and the Sun, and the area between points H, I and the Sun?

• The area between A, B and the Sun is the largest.
• The area between H, I and the Sun is the largest
• Both areas are equal in size
• There is not enough information to determine the areas

Multiple Choice

What has an eccentricity of zero

• a straight line
• a large ellipse
• a circle
• a small ellipse

Multiple Choice

A planet moves __________ when it is farthest from the sun.

• faster
• slower

Multiple Choice

Kepler's first law states that the orbits of the planets are oval in shape or 

• ellipses
• perfect circles

Multiple Choice

The path a planet travels around the sun is called its 

• orbit
• ellipse
• barycenter
• precession

Multiple Choice

When do planets move the fastest?

• Close to the sun
• Far away from the sun

Multiple Choice

Which is NOT one of Kepler's laws?

• Planets travel in an ellipse
• Planets closest to the sun travel faster
• The farther a planet is from the sun, the longer it takes to orbit
• Planets revolve around the Earth

Multiple Choice

What is at the middle of a Heliocentric system?

• Mars

• Moon

• Sun

• Earth

Multiple Choice

Who proposed the Heliocentric system?

• Copernicus

• Ptolemy

• Aristotle

• Galileo

Multiple Choice

What does the Geocentric system look like?

Multiple Choice

Complete the following statement: The farther away two planets are the _______ the gravitational force between them.

• greater
• same
• zero
• less

Multiple Choice

Which term describes when the Earth spins on its axis.

• Rotation
• Revolution
• Kepler's Laws
• Precession

Multiple Choice

The period of the earth's orbit around the sun is ____.

• 1 day
• 1 year
• 24 hours
• 364 hours