Charles Hakes Fort Lewis College2 Chapter 1 Kepler’s Laws

Charles HakesFort Lewis College 2

Chapter 1

Kepler’s Laws


Outline

• Logistics• Lab notes• Review• Kepler’s Laws


Logistics

• Read about Newton (1.4).


Lab notes

• Sunset Part 2• Due ASAP• Important - Attach part 1!• update sketch if necessary• sketch both sunsets on the same plot

• Do Kepler small group for Friday.• Due Friday at 5:30 P.M.• In box outside room 671.


I read the section on Kepler’s laws.

A) True B) False


Planetary orbits are

A) Circular.

B) Parabolic.

C) Elliptical.

D) Hyperbolic.


Planetary orbits are

A) Circular.

B) Parabolic.

C) Elliptical.

D) Hyperbolic.


Two planets have orbits with the same periods. Which is true?

A) Their velocities must be the same.

B) They must have the same eccentricity.

C) They must have the same semi-major axis.

D) Their orbits must be identical.


Two planets have orbits with the same periods. Which is true?

A) Their velocities must be the same.

B) They must have the same eccentricity.

C) They must have the same semi-major axis.

D) Their orbits must be identical.


Figure 1.15Johannes Kepler (1571-1630)


Kepler Overview

• Theoretician• Used observations of Tycho Brahe• Wanted a unifying principle to explain the motions

of the planets without epicycles.• Took ~29 years, but he did it.


Figure 1.16Tycho Brahe


Kepler’s “Laws”

• http://faculty.fortlewis.edu/hakes_c/

• Allow pop-up windows!

http://faculty.fortlewis.edu/hakes_c/



• That “shape” law• Orbits are elliptical, with the Sun at one focus.




• That “speed” law• (A line between the Sun and a)Planet sweeps

out (in the ellipse) equal areas in equal times.




• That “speed” law• (A line between the Sun and a)Planet sweeps

out equal areas (of the ellipse) in equal times.• That “math” law

P2 (years) = a3 (astronomical units)


A planet orbit could be circular.

A) True

B) False


A planet orbit could be circular.

A) True

B) False


Two planets have orbits with the same sized semi-major axis. Which is true?

A) The planet with the most eccentric orbit moves faster all the time.

B) The planet with the most eccentric orbit moves faster some of the time.

C) The planet with the most eccentric orbit never moves faster.

D) Not enough information to answer.


Two planets have orbits with the same sized semi-major axis. Which is true?

A) The planet with the most eccentric orbit moves faster all the time.

B) The planet with the most eccentric orbit moves faster some of the time.

C) The planet with the most eccentric orbit never moves faster.

D) Not enough information to answer.


Assume a planet orbits exactly twice as far from the Sun as the Earth does.

A) It’s period is 2 years exactly.

B) It’s period is between 2 and 3 years

C) It’s period is between 3 and 4 years

D) It’s period is 4 years exactly.


Assume a planet orbits exactly twice as far from the Sun as the Earth does.

A) It’s period is 2 years exactly.

B) It’s period is between 2 and 3 years

C) It’s period is between 3 and 4 years

D) It’s period is 4 years exactly.


Three Minute Paper

• Write 1-3 sentences.• What was the most important thing

you learned today?• What questions do you still have

about today’s topics?


Three Minute Paper

• Answer this question (without discussion):

• What is the air-speed velocity of an unladen swallow?

Documents

Charles Hakes Fort Lewis College2 Chapter 1 Kepler’s Laws