Question 1

How far must one travel to escape Earth's gravitational field?
A)to a region above Earth's atmosphere
B)to a region well beyond the Moon
C)to a region beyond the solar system
D)forget it; you can't travel far enough.

Accepted Answer

Earth's gravitational field extends infinitely into space, decreasing in strength with distance but never reaching zero. Therefore, one cannot completely escape Earth's gravitational influence.

Question 2

If the Sun collapsed to a black hole, Earth's gravitational attraction to it would be
A)more.
B)less.
C)the same.

Accepted Answer

The gravitational attraction of the Sun on Earth is dependent on its mass and distance. If the Sun collapsed to a black hole, its mass would remain the same but its distance from Earth would also remain the same. Therefore, the gravitational attraction between Earth and the Sun (now a black hole) would remain the same.

Question 3

An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be
A)zero.
B)40 N.
C)120 N.
D)360 N.
E)1080 N.

Accepted Answer

The force exerted by the asteroid on the spacecraft depends on the mass and distance between them. As the spacecraft moves to a position three times as far from the center of the asteroid, the distance between them increases by 3 times. According to the inverse square law of gravitation, the force of gravity decreases by a factor of 3^2 = 9. Therefore, the force will be (360 N)/9 = 40 N. So, the best choice is B.

Question 4

Half-way to the center of a completely hollow planet with a thin uniform shell, your weight would be
A)one-quarter of your weight on the surface.
B)one-half of your weight on the surface.
C)three-quarters of your weight on the surface.
D)the same as at the surface.
E)zero.

Accepted Answer

Inside a hollow sphere, the gravitational forces exerted by the shell cancel out at any point within the shell due to symmetry, resulting in zero net gravitational force and thus zero weight.

Question 5

Each of us weighs a tiny bit less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper because the
A)gravitational field is shielded inside the building.
B)mass of the building above slightly attracts us upward.
C)both of these
D)neither of these

Accepted Answer

The mass of the skyscraper above us exerts a gravitational force that slightly pulls us upward, resulting in a slightly decreased weight inside the building. The gravitational field is not shielded inside the building, as gravity permeates all matter. Thus, option B is the correct answer.

Question 6

If you drop a stone into a hole drilled all the way to the other side of Earth (neglect the molten core), the stone will
A)come to an abrupt stop at Earth's center.
B)speed up until it gets to Earth's center.
C)speed up until it reaches Earth's other side.
D)slow down until it reaches Earth's center.

Accepted Answer

The stone will speed up due to gravity until it reaches Earth's center, where its speed is maximum due to the accumulation of gravitational acceleration.

Question 7

A black hole is
A)an empty region of space with a huge gravitational field.
B)at the center if all stars.
C)the remains of a giant star that has undergone gravitational collapse.

Accepted Answer

A black hole is the remains of a giant star that has undergone gravitational collapse. Its gravitational field is so strong that nothing, not even light, can escape it. It is not an empty region of space or at the center of all stars.

Question 8

Planets wobble in their orbits due to
A)the gravitational attraction to other planets.
B)uncertainties in the inverse-square law.
C)elliptical-orbit quirks.
D)all of the above
E)none of the above

Accepted Answer

Planets wobble in their orbits primarily due to the gravitational attractions of other planets. This gravitational pull from neighboring planets can cause slight variations in a planet's orbit, leading to what is observed as a wobble.

Question 9

The factor most directly responsible for making a black hole invisible is its
A)size.
B)mass.
C)color.
D)surface escape velocity.
E)none of the above

Accepted Answer

Surface escape velocity, also known as the speed required for an object to escape the gravitational pull of a massive body, is directly related to the mass of the body. A black hole's mass is so large that its surface escape velocity is greater than the speed of light. Therefore, nothing, including light, can escape from a black hole's gravitational pull making it appear invisible.

Question 10

A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive spaceship lands on the planet's surface, inhabitants find that the gravitational field inside the planet is
A)still zero.
B)non-zero, directed toward the spaceship.
C)non-zero, directed away from the spaceship.

Accepted Answer

The gravitational field inside the hollow spherical planet is zero due to the principle of superposition, which states that the gravitational field inside a hollow spherical shell is zero. However, when a very massive spaceship lands on the planet's surface, it creates a non-zero gravitational field inside the planet, directed toward the spaceship. This is because the spaceship's mass is not distributed symmetrically throughout the planet, and therefore creates an uneven distribution of mass which results in a non-zero gravitational field inside the planet.

Question 11

Earth is presently accelerating toward the Sun (centripetal acceleration). If the Sun collapsed into a black hole, this acceleration would
A)increase.
B)decrease.
C)remain the same.
D)cease to exist.

Accepted Answer

The acceleration would remain the same because the gravitational force between two objects depends on their masses and the distance between them. If the Sun were to collapse into a black hole without losing mass, the Earth's orbit and the gravitational force exerted on it would not change, hence the acceleration would remain the same.

Question 12

If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would
A)be the same.
B)double.
C)quadruple.
D)be eight times as much as now.
E)none of the above

Accepted Answer

Your weight is determined by the gravitational force between you and the Earth. If both your mass and Earth's mass double, the gravitational force (and thus your weight) would quadruple, as gravitational force is proportional to the product of the two masses.

Question 13

The amount of gravitational force that acts on a space vehicle while in Earth orbit is
A)nearly zero.
B)nearly as much as the vehicle's weight on Earth's surface.
C)the same as the vehicle's weight on Earth's surface.

Accepted Answer

In Earth orbit, a space vehicle is in free fall, experiencing microgravity. However, the gravitational force acting on it is nearly as much as its weight on Earth's surface. The sensation of weightlessness is due to the vehicle and its contents falling at the same rate towards Earth, not because gravity is significantly weaker.

Question 14

Half-way to the center of a planet of uniform density, your weight compared to that at the surface would be
A)one-quarter.
B)one-half.
C)three-quarters.
D)the same as at the surface.
E)zero.

Accepted Answer

According to the inverse square law, the force of gravity decreases as the square of the distance between two objects increases. This means that the further you are from the center of the planet, the weaker gravity is. At the halfway point, you are twice as far from the center as you are at the surface, so gravity is four times weaker. Since weight is the force of gravity on an object, your weight would be one-half of what it is at the surface. Therefore, the best choice is B (one-half).

Question 15

The force of gravity acting on you will increase if you
A)burrow deep inside Earth.
B)stand on a planet with a shrinking radius.
C)both of these
D)neither of these

Accepted Answer

Standing on a planet with a shrinking radius increases the gravitational force because gravity is inversely proportional to the square of the distance from the center of the planet.

Question 16

Rate this statement: No force due to Earth's gravity acts on astronauts inside the orbiting space station.
A)always true while in orbit
B)sometimes true while in orbit
C)always false

Accepted Answer

Astronauts inside an orbiting space station experience microgravity because they are in free fall around the Earth, not because Earth's gravity doesn't act on them. Earth's gravity keeps the space station in orbit and affects everything inside it.

Question 17

If an object is placed exactly halfway between Earth and the Moon, it would fall toward the
A)Earth.
B)Moon.
C)neither of these

Accepted Answer

The gravitational force exerted by Earth is stronger than that of the Moon due to Earth's larger mass, so the object would fall toward Earth.

Question 18

An outcome of universal gravitation is that
A)planets aren't cubes with sharp corners.
B)its discovery prompted other laws of nature.
C)prediction and discovery of planets.
D)all of the above

Accepted Answer

Universal gravitation has led to the prediction and discovery of planets, as well as prompting the development of other laws of nature. It also explains why planets, and other celestial bodies, are not perfect cubes with sharp corners, but instead have irregular shapes.

Question 19

Which rocket would require more fuel?
A)one going from the Moon to Earth.
B)one going from Earth to the Moon.
C)both the same.

Accepted Answer

A rocket going from Earth to the Moon would require more fuel because it has to overcome Earth's gravitational pull, which is much stronger than the Moon's. This requires more energy to escape the Earth's atmosphere and gravitational pull. Once the rocket is on its way and has left Earth's gravity well, it would encounter much less resistance and require less fuel to continue to the Moon.

Question 20

When a star collapses to form a black hole, its mass
A)increases.
B)decreases.
C)remains the same.

Accepted Answer

The mass of a star remains the same when it collapses to form a black hole. The process changes its volume and density, not its mass.

Quiz 9: Gravity

How far must one travel to escape Earth's gravitational field?

If the Sun collapsed to a black hole, Earth's gravitational attraction to it would be

An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be

Half-way to the center of a completely hollow planet with a thin uniform shell, your weight would be

Each of us weighs a tiny bit less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper because the

If you drop a stone into a hole drilled all the way to the other side of Earth (neglect the molten core) , the stone will

A black hole is

Planets wobble in their orbits due to

The factor most directly responsible for making a black hole invisible is its

A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive spaceship lands on the planet's surface, inhabitants find that the gravitational field inside the planet is

Earth is presently accelerating toward the Sun (centripetal acceleration) . If the Sun collapsed into a black hole, this acceleration would

If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would

The amount of gravitational force that acts on a space vehicle while in Earth orbit is

Half-way to the center of a planet of uniform density, your weight compared to that at the surface would be

The force of gravity acting on you will increase if you

Rate this statement: No force due to Earth's gravity acts on astronauts inside the orbiting space station.

If an object is placed exactly halfway between Earth and the Moon, it would fall toward the

An outcome of universal gravitation is that

Which rocket would require more fuel?

When a star collapses to form a black hole, its mass