Ay [T6.5] - Kepler's Laws

Question 1

Name law 1 of the 3 laws of planetary motion

Answer 1

The orbit of all the planets is an ellipse with the sun at one foci.

Question 2

Name law 2 of the 3 laws of planetary motion

Answer 2

An imaginary line connecting the planet to the sun “sweeps out” equal areas in equal times

Question 3

Name law 3 of the 3 laws of planetary motion

Answer 3

The square of the orbital period is proportional to the cube of it’s mean distance from the sun

T²∝R³

Question 4

Define aphelion

Answer 4

The furthest point from the sun on an orbit

Question 5

Define perihelion

Answer 5

The closest point to the sun on an orbit

Question 6

Define eccentricity

Answer 6

A measure of how stretched an elliptical orbit is

Question 7

What are foci points in an elliptical orbit?

Answer 7

In an elliptical orbit, the two foci (plural of focus) are the two points used to draw the ellipse

Question 8

When is the aphelion for Earth’s orbit?

Answer 8

In the summer

Question 9

When is the perihelion for Earth’s orbit?

Answer 9

In the winter

Question 10

In the 2nd law of the 3 laws of planetary motion, where is a celestial body in it’s orbit moving the slowest and where is it moving the fastest?

Answer 10

Closer to the object that it’s orbiting, the celestial body moves quicker. (It’ll have the most kinetic energy here.)

Further away from the object that it’s orbiting, the celestial body moves slower. (It’ll have the least kinetic energy here.)

Question 11

What is the equation related to Kepler’s 3rd law for anything that orbits the sun?

Answer 11

T(y)² / R(AU)³ = 1

T measured in years (y)
R measured in AU

Question 12

If T² / R³ = k, and you’re using the data of 2 objects that orbit the same object, what can you do?

Answer 12

If constant doesn’t change, you can remove it.

(T1²) / (R1³) = (T2²) / (R2³)

Question 13

The k in Kepler’s 3rd law depends on what?

Answer 13

The mass of the central object - the bigger the mass, the smaller k is

Question 14

What is the ratio of masses equations for Kepler’s 3rd law?

Answer 14

k1 / k2 = m2 / m1

1 = the sun
2 = the new star

Question 15

In Newton’s Universal Law of Gravitation, the size of the force acting between bodies depends on what things?

Answer 15

The mass of each body in the situation

The distance between the two bodies

Question 16

In Newton’s Law of Universal Gravitation, what is force proportional to (both words and equations)?

Answer 16

Force is directly proportional to both masses of both objects, and force is inversely proportional to distance squared

F ∝ (m1 × m2) / r²