Question 1

The distance between Earth and the Moon:

Accepted Answer

A) will never change 
B) is slowly decreasing 
C) is slowly increasing 
D) will increase or decrease depending on future changes in the tides on the Moon due to the Earth 
E) will increase or decrease depending on future changes in the tides on the Earth due to the Moon 
A) will never change 
B) is slowly decreasing 
C) is slowly increasing 
D) will increase or decrease depending on future changes in the tides on the Moon due to the Earth 
E) will increase or decrease depending on future changes in the tides on the Earth due to the Moon C

Question 2

How much stronger is the gravitational force of the Sun on the Earth compared to the gravitational force of the Sun on Pluto? Note that Pluto's semimajor axis is 40,AU,and Pluto's mass is 0.002 times the mass of the Earth.

Accepted Answer

For a planet,the force of gravity between it and the Sun is F = GM_SunM/d²;thus F_P/F_E = (GM_SunM_P/d_P²)/(GM_SunM_E/d_E²) = (M_P/M_E)× (d_E/d_P)² 0.002 × (1/40)² 0.002 / 40² = 1.3 × 10⁶.Therefore the force of gravity between the Sun and Pluto is about a million times less than that between the Sun and the Earth.

Question 3

If we wanted to increase the Hubble Space Telescope's altitude above the Earth and keep it in a stable orbit,we also would need to:

Accepted Answer

A) increase its orbital speed 
B) increase its weight 
C) decrease its weight 
D) decrease its orbital speed 
E) increase its mass 
A) increase its orbital speed 
B) increase its weight 
C) decrease its weight 
D) decrease its orbital speed 
E) increase its mass D

Question 4

Which is larger,the tidal force on the Earth due to the Moon or the tidal force on the Earth due to the Sun,and by approximately how much? Explain conceptually why this is possible given that the gravitational force of the Sun on the Earth is 200 times larger than the gravitational force of the Moon on the Earth.

Accepted Answer

Tides are caused by the difference betwe

Question 5

Lunar tides are approximately _________ solar tides.

Accepted Answer

A) 2 times weaker than 
B) 2 times stronger than 
C) 200 times weaker than 
D) 200 times stronger than 
E) the same strength as 
A) 2 times weaker than 
B) 2 times stronger than 
C) 200 times weaker than 
D) 200 times stronger than 
E) the same strength as

Question 6

You find a moon orbiting a planet.The moon has a period of 10 days,and the average distance between the moon and planet is 106 km.What is the planet's mass? Note that the mass of Jupiter is 1.9 × 1027 kg.

Accepted Answer

A) 0.1 MJupiter 
B) 0.4 MJupiter 
C) 1 MJupiter 
D) 4 MJupiter 
E) 10 MJupiter 
A) 0.1 MJupiter 
B) 0.4 MJupiter 
C) 1 MJupiter 
D) 4 MJupiter 
E) 10 MJupiter

Question 7

_________ hypothesized that planetary motions could be explained by a force arising from the attraction between the mass of the planet and Sun that decreased with the square of the distance between them.

Accepted Answer

A) Johannes Kepler 
B) Isaac Newton 
C) Tycho Brahe 
D) Nicolaus Copernicus 
E) Galileo Galilei 
A) Johannes Kepler 
B) Isaac Newton 
C) Tycho Brahe 
D) Nicolaus Copernicus 
E) Galileo Galilei

Question 8

In a system with three gravitating bodies,there are _________ stable locations called _________ points for the third object to orbit in lockstep with the two more massive objects.

Accepted Answer

A) 3;tidal 
B) 2;tidal 
C) 4;Roche 
D) 2;Lagrange 
E) 5;Lagrange 
A) 3;tidal 
B) 2;tidal 
C) 4;Roche 
D) 2;Lagrange 
E) 5;Lagrange

Question 9

Tidal forces can affect:

Accepted Answer

A) moons 
B) galaxies 
C) planets 
D) satellites 
E) all of the above 
A) moons 
B) galaxies 
C) planets 
D) satellites 
E) all of the above

Question 10

Astronauts orbiting Earth in the space shuttle feel weightless in space because:

Accepted Answer

A) they are farther away from the Earth 
B) they eat less food while in orbit 
C) the gravitational pull of the Moon counteracts the Earth's gravitational pull 
D) they are in constant free fall around the Earth 
E) they are in space where there is no gravity 
A) they are farther away from the Earth 
B) they eat less food while in orbit 
C) the gravitational pull of the Moon counteracts the Earth's gravitational pull 
D) they are in constant free fall around the Earth 
E) they are in space where there is no gravity

Question 11

If a satellite sent to Mars is designed to return a rock sample to Earth,how fast must the satellite be launched from its surface in order to escape Mars's gravity? For reference,Mars has a mass of 6 × 1023 kg and a radius of 3,400 km.

Accepted Answer

A) 100 m/s 
B) 5,000 m/s 
C) 20 m/s 
D) 20,000 m/s 
E) You must know the mass of the satellite to determine the answer. 
A) 100 m/s 
B) 5,000 m/s 
C) 20 m/s 
D) 20,000 m/s 
E) You must know the mass of the satellite to determine the answer.

Question 12

Two rocks (call them S and T)are released at the same time from the same height and start from rest.Rock S has 20 times the mass of rock T.Which rock will fall faster if the only forces involved are each rock's mutual gravitational attraction with Earth?

Accepted Answer

A) Rock S 
B) Rock T 
C) Both rocks will fall at the same rate. 
D) not enough information is available to answer 
A) Rock S 
B) Rock T 
C) Both rocks will fall at the same rate. 
D) not enough information is available to answer

Question 13

Suppose you are suddenly transported to a planet that had 1/4 the radius of Earth but the same mass as the Earth.Your weight would _________ by a factor of _________.

Accepted Answer

A) increase;4 
B) increase;16 
C) decrease;4 
D) decrease;16 
E) decrease;8 
A) increase;4 
B) increase;16 
C) decrease;4 
D) decrease;16 
E) decrease;8

Question 14

Because of the tidal force between the Earth and Moon:

Accepted Answer

A) the Earth's rotation rate is decreasing 
B) the Moon's distance from Earth is increasing 
C) the Moon's orbital period is increasing 
D) the Moon's rotational period is increasing 
E) All of the above are true. 
A) the Earth's rotation rate is decreasing 
B) the Moon's distance from Earth is increasing 
C) the Moon's orbital period is increasing 
D) the Moon's rotational period is increasing 
E) All of the above are true.

Question 15

Show that the gravitational pull on Earth from the Sun is about 200 times the gravitational pull on Earth from the Moon.For reference,Moon's mass is 7.3 × 10 22 kg,the Sun's mass is 2 × 1030 kg,the Earth-Moon distance is 3.8 × 105 km,and the Earth-Sun distance is 1.5 × 108 km.

Accepted Answer

F_grav = GM₁M₂/r²;thus F_Sun/F_Moon = (GM_SM_E/d_ES²)/(

Question 16

Show that the tidal force on Earth from the Moon is approximately two times the tidal force on Earth from the Sun.For reference,Moon's mass is 7.3 ×1022 kg,the Sun's mass is 2 × 1030 kg,the Earth-Moon distance is 3.8 × 105 km,and the Earth-Sun distance is 1.5 × 108 km.

Accepted Answer

The tidal force on the Earth due to a bo

Question 17

The force of gravity between the Earth and the Sun is _________ the force of gravity between the Earth and the Moon.For reference,the average distance between the Earth and the Moon is 0.003 AU,the mass of the Moon is 7 × 1022 kg,and the mass of the Sun is 2 × 1030 kg.

Accepted Answer

A) 86,000 times larger than 
B) 260 times larger than 
C) 140 times smaller than 
D) 6,400 times smaller than 
E) the same as 
A) 86,000 times larger than 
B) 260 times larger than 
C) 140 times smaller than 
D) 6,400 times smaller than 
E) the same as

Question 18

The tidal force on the Earth due to the Moon is about two times stronger than that due to the Sun.

Accepted Answer

A) True 
 B)False

Question 19

An astronaut orbiting the Earth in a circular orbit at a constant speed does not feel the force of gravity because his or her acceleration is zero.

Accepted Answer

A) True 
 B)False

Question 20

The distance between Earth and the Moon is increasing because of:

Accepted Answer

A) the expansion of the Universe 
B) the expansion of the Solar System 
C) tidal forces from the Moon 
D) tidal forces from the Moon and Sun 
E) dark energy 
A) the expansion of the Universe 
B) the expansion of the Solar System 
C) tidal forces from the Moon 
D) tidal forces from the Moon and Sun 
E) dark energy

Exam 4: Gravity and Orbits

The distance between Earth and the Moon:

How much stronger is the gravitational force of the Sun on the Earth compared to the gravitational force of the Sun on Pluto? Note that Pluto's semimajor axis is 40,AU,and Pluto's mass is 0.002 times the mass of the Earth.

If we wanted to increase the Hubble Space Telescope's altitude above the Earth and keep it in a stable orbit,we also would need to:

Lunar tides are approximately _________ solar tides.

You find a moon orbiting a planet.The moon has a period of 10 days,and the average distance between the moon and planet is 106 km.What is the planet's mass? Note that the mass of Jupiter is 1.9 × 1027 kg.

_________ hypothesized that planetary motions could be explained by a force arising from the attraction between the mass of the planet and Sun that decreased with the square of the distance between them.

In a system with three gravitating bodies,there are _________ stable locations called _________ points for the third object to orbit in lockstep with the two more massive objects.

Tidal forces can affect:

Astronauts orbiting Earth in the space shuttle feel weightless in space because:

If a satellite sent to Mars is designed to return a rock sample to Earth,how fast must the satellite be launched from its surface in order to escape Mars's gravity? For reference,Mars has a mass of 6 × 1023 kg and a radius of 3,400 km.

Two rocks (call them S and T)are released at the same time from the same height and start from rest.Rock S has 20 times the mass of rock T.Which rock will fall faster if the only forces involved are each rock's mutual gravitational attraction with Earth?

Suppose you are suddenly transported to a planet that had 1/4 the radius of Earth but the same mass as the Earth.Your weight would _________ by a factor of _________.

Because of the tidal force between the Earth and Moon:

Show that the gravitational pull on Earth from the Sun is about 200 times the gravitational pull on Earth from the Moon.For reference,Moon's mass is 7.3 × 10 22 kg,the Sun's mass is 2 × 1030 kg,the Earth-Moon distance is 3.8 × 105 km,and the Earth-Sun distance is 1.5 × 108 km.

Show that the tidal force on Earth from the Moon is approximately two times the tidal force on Earth from the Sun.For reference,Moon's mass is 7.3 ×1022 kg,the Sun's mass is 2 × 1030 kg,the Earth-Moon distance is 3.8 × 105 km,and the Earth-Sun distance is 1.5 × 108 km.

The force of gravity between the Earth and the Sun is _________ the force of gravity between the Earth and the Moon.For reference,the average distance between the Earth and the Moon is 0.003 AU,the mass of the Moon is 7 × 1022 kg,and the mass of the Sun is 2 × 1030 kg.

The tidal force on the Earth due to the Moon is about two times stronger than that due to the Sun.

An astronaut orbiting the Earth in a circular orbit at a constant speed does not feel the force of gravity because his or her acceleration is zero.

The distance between Earth and the Moon is increasing because of:

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornments Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

You find a moon orbiting a planet.The moon has a period of 10 days,and the average distance between the moon and planet is 10⁶ km.What is the planet's mass? Note that the mass of Jupiter is 1.9 × 10²⁷ kg.

In a system with three gravitating bodies,there are _ stable locations called _ points for the third object to orbit in lockstep with the two more massive objects.

If a satellite sent to Mars is designed to return a rock sample to Earth,how fast must the satellite be launched from its surface in order to escape Mars's gravity? For reference,Mars has a mass of 6 × 10²³ kg and a radius of 3,400 km.

Suppose you are suddenly transported to a planet that had 1/4 the radius of Earth but the same mass as the Earth.Your weight would _ by a factor of _.

Show that the gravitational pull on Earth from the Sun is about 200 times the gravitational pull on Earth from the Moon.For reference,Moon's mass is 7.3 × 10 ²² kg,the Sun's mass is 2 × 10³⁰ kg,the Earth-Moon distance is 3.8 × 10⁵ km,and the Earth-Sun distance is 1.5 × 10⁸ km.

Show that the tidal force on Earth from the Moon is approximately two times the tidal force on Earth from the Sun.For reference,Moon's mass is 7.3 ×10²² kg,the Sun's mass is 2 × 10³⁰ kg,the Earth-Moon distance is 3.8 × 10⁵ km,and the Earth-Sun distance is 1.5 × 10⁸ km.

The force of gravity between the Earth and the Sun is _________ the force of gravity between the Earth and the Moon.For reference,the average distance between the Earth and the Moon is 0.003 AU,the mass of the Moon is 7 × 10²² kg,and the mass of the Sun is 2 × 10³⁰ kg.