Kepler's Laws of Planetary Motion

Question 1

What is the path around the sun?

Answer 1

An ellipse

Question 2

What is the shape of the path of each planet around the sun?

Answer 2

An oval shape

Question 3

What is in the ellipse?

Answer 3

Two foci/points

Question 4

What determines the shape of the ellipse?

Answer 4

The foci; the farther apart they are, the more elongated the ellipse is

Question 5

What do ellipses have?

Answer 5

Eccentricity

Question 6

What is eccentricity?

Answer 6

The measurement of how elongated a closed circle is

Question 7

How is eccentricity measured?

Answer 7

In values of 0.1 to 1

Question 8

What is the eccentricity of a perfect circle?

Answer 8

Zero

Question 9

What is the rule of ellipses?

Answer 9

The greater the value, the more elongated the ellipse is

Question 10

How is eccentricity calculated?

Answer 10

Eccentricity = Distance between foci divided by length of major axis (E = d / L)

Question 11

What originally prompted Kepler’s 2nd Law of Planetary Motion?

Answer 11

Kepler noticed that the speed of Mars in its orbit changes in predictable ways

Question 12

What is perihelion?

Answer 12

The point in a planet’s orbit closest to the sun

Question 13

What is Earth’s perihelion?

Answer 13

147 million kilometers, and occurs annually on January 3rd

Question 14

What is aphelion?

Answer 14

The point in a planet’s orbit farthest away from the sun

Question 15

What is Earth’s aphelion?

Answer 15

152 million kilometers, and occurs annually on July 4th

Question 16

What is the sun’s imaginary line?

Answer 16

Each planet revolves around an imaginary line so that the sun sweeps over equal areas in each time intervals

Question 17

What does this imaginary line mean?

Answer 17

Planets must move faster at perihelion and slower at aphelion

Question 18

Why do planets move faster at perihelion?

Answer 18

The sun’s gravity pulls stronger on the planet when it’s closest to it, causing faster movement

Question 19

Why do planets move slower at aphelion?

Answer 19

The sun’s gravity decreases as the distance between it and the planet, causing slower movement

Question 20

What is the rule for orbital period?

Answer 20

The closer a planet is to the sun, the shorter the orbital period

Question 21

What is an orbital period?

Answer 21

The time it takes for a planet to complete one orbit around the sun in Earth years

Question 22

What is the orbital period squared?

Answer 22

Orbital period squared = its mean solar distance cubed (T^2 = d^3)

Question 23

What is the distance of Earth from the sun?

Answer 23

93 million miles/1 astronomical unit

Question 24

What are astronomical units?

Answer 24

Units used to measure distances in our solar system