Chapter 2 Questions

Front 1

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

Back 1

elliptical, not circular.

Front 2

Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was:

Back 2

his detailed and accurate observations of the planet's position.

Front 3

A circular orbit would have an eccentricity of:

Back 3

0

Front 4

Upon which point do Copernicus and Kepler disagree?

Back 4

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

Front 5

According to Kepler's third law, the square of the planet's period in years is:

Back 5

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

Front 6

What does Kepler's third law imply about planetary motion?

Back 6

Planets further from the Sun orbit at a slower speed than planets closer to the Sun.

Front 7

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

Front 8

A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's

Back 8

third law of planetary distances.

Front 9

An asteroid with an orbit lying entirely inside Earth's

Back 9

has an orbital semimajor axis of less than 1 AU.

Front 10

If Earth's orbit around the Sun were twice as large as it is now, the orbit would take

Back 10

more than two times longer to traverse

Front 11

Today we rely largely on what technique to precisely measure distances in the solar system?

Back 11

radar echo timings

Front 12

The force of gravity varies with the

Back 12

both product of the two masses and inverse square of the distance separating the two bodies

Front 13

The Law of Universal Gravitation was developed by

Back 13

Newton.

Front 14

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:

Back 14

decrease by a factor of 9.

Front 15

How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU?

Back 15

100X

Front 16

Which of these was a contribution of Newton to astronomy?

Back 16

-The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up.

-His differential calculus lets us calculate planetary motions more accurately.

-The Moon pulls as strongly on us as we do on it.

-Artificial satellites could be put into orbit about the Earth

Front 17

Geosynchronous satellites orbit at about four Earth radii, where the Earth's gravitational pull is

Back 17

1/16 g.

Front 18

Jupiter lies about 5 A.U. from the Sun, so at its distance:

Back 18

the Sun's gravity is 25 times weaker than its pull on the Earth.

Front 19

Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh:

Back 19

the same as you do here

Front 20

If the distance between two asteroids is doubled, the gravitational force they exert on each other will

Back 20

be one fourth as great.

Front 21

Newton's Law of Gravity would explain why Saturn, so far from the Sun, moves so slowly across the sky.

Back 21

true

Front 22

Compared to orbital velocity, escape velocity is about:

Back 22

40% more.

Front 23

Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by

Back 23

the mass of both the planet and the Sun and the distance between the two.

Front 24

Escape velocity is the speed required to:

Back 24

overcome the gravitational pull of an object.

Front 25

If the Sun and its mass were suddenly to disappear, Earth would

Back 25

fly off into space

Front 26

Figure 2.26(b) in the textbook ("Orbits") shows the orbits of two stars of unequal masses. If one star has twice the mass of the other, then the more massive star

Back 26

moves more slowly than the less massive star.

Front 27

Two otherwise isolated bodies of equal mass will orbit in which of the following configurations as viewed from a fixed distant point?

Back 27

They would orbit each other in identical but oppositely directed ellipses that share a common focus.

Front 28

In what way did Newton improve Kepler's laws?

Back 28

He discovered the dependence on mass in the third law.

Front 29

According to Newton, planets orbit in ellipses with what at the two foci?

Back 29

The center of mass and nothing