Chapter #3

Question 1

Which was a contribution to astronomy made by Copernicus?

Answer 1

He laid out the order and relative motion of the known solar system

Question 2

Which of these was NOT a part of the original Copernican model?

Answer 2

Mercury speeds up at perihrlion, and slows down at aphelion

Question 3

Kepler’s first law worked, where Copernicus’ original heliocentric model failed, because Kepler described the orbit as:

Answer 3

elliptical, not circular

Question 4

Tycho Brahe’s contribution to Kepler’s Laws of Planetary Motion was

Answer 4

his detailed and accurate observations of the planet’s position

Question 5

Upon which point do Copernicus and Kepler disagree?

Answer 5

the orbits of the planets are ellipses, with one focus at the Sun

Question 6

Which concept was NOT a part of Kepler’s Laws of Planetary Motion?

Answer 6

epicycles are needed to explain the varying brightness of the planets.

Question 7

According to Kelper’s third law, the square of the planet’s period in years is

Answer 7

proportional to the cube of its semimajor axis in A.U

Question 8

The Ptolemaic model probably persisted for all these reasons EXCEPT

Answer 8

it accounted well for Galileo’s observations of the phase cycle of Venus.

Question 9

A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years?

Answer 9

square root of 27

Question 10

The place in a planet’s orbit that is closer to the Sun is called

Answer 10

perihelion

Question 11

The Law of Universal Gravitation was developed by

Answer 11

Newton

Question 12

The force of gravity between two objects

Answer 12

increase with the masses of the bodies, but decreases with the square of the distances between them

Question 13

According to Newton’s Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would:

Answer 13

decreases by a factor of 9

Question 14

Which of these was a contribution of Newton to astronomy?

Answer 14

All of these were due to Newton’s work

Question 15

How does Newton’s Universal Law of Gravitation explain Kepler’s laws

Answer 15

• Universal gravitation implies that the planets further from the Sun will move more slowly than the planets closer to the Sun
• Universal gravitation implies that when a planet is closer to the Sun in its orbit, it will move faster than when it is farther from the Sun