Kepler's Laws of Planetary Motion

Question 1

Johannes Kepler:

Answer 1

• German mathematician and astronomer
• Postulated the 3 laws of planetary motion based upon heliocentric model of solar system
• His model explains motions of the earth and celestial objects

Question 2

Kepler’s First Law:

Answer 2

• The orbit of a planet about a star is an ellipse with the star at one focus
• The star is considered a primary and the planet a satellite

Question 3

Parts of an Ellipse:

Answer 3

• Sun at one focus
• Other focus
• Planet
• Major axis
• Path of orbit

Question 4

Ellipse Values:

Answer 4

• Value calculated is between 0 and 1
• Example: (0.007, must have zero at front)
• 0= most circular
• 1= most elliptical

Question 5

Kepler’s Second Law:

Answer 5

The radius between a satellite (such as a planet) and it’s primary (such as the sun) sweeps out equal areas in equal times

Question 6

Kepler’s Third Law:

Answer 6

• The closer a satellite is to it’s primary, the faster it moves in its orbit
• The closest planets move the fastest.

Question 7

Sir Isaac Newton:

Answer 7

-Used Kepler’s Laws in developing his ideas on gravity

Question 8

Newton’s ideas:

Answer 8

1. Gravity is a force of attraction between objects

2. It is dependent upon the mass of the object and the distance between the objects

Question 9

What is weight dependent on?

Answer 9

The amount of matter in an object and the gravitational pull upon that object

Question 10

The elliptical shape of orbits is due to what two forces?

Answer 10

Gravity and inertia

Question 11

The faster a planet orbits its primary us due to its?

Answer 11

Closeness to the primary and its mass and the mass of the primary

Question 12

Circular orbits have?

Answer 12

Equal gravitational and inertial forces

Question 13

Elliptical orbits have? Why?

Answer 13

• Unequal gravitational and inertial forces

- The force of gravity pulls the planet around its focus faster when it is closer, and slower when its further away