Free Practice Quiz Question List

7 Gravitation and Orbits Online Quiz Questions

Use this free practice quiz with 20 questions to review 7 Gravitation and Orbits, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

If the distance between two objects is doubled while their masses remain unchanged, the gravitational force between them becomes one-fourth as large.

A
True
B
False

True or false

1 point

The gravitational field produced by a spherical body points radially outward from its center.

A
True
B
False

Fill in the blank

1 point

Outside an extended, spherically symmetric body, its gravitational effect is the same as if its mass were concentrated at its .

Written response

1 point

A point is at distance $R$ from the center of a spherical body. What is the ratio of the gravitational-field magnitude at distance $2R$ to the magnitude at distance $R$ ?

Choose one

1 point

For an isolated pair of masses, gravitational potential energy is defined to be zero at infinite separation. What does a negative potential energy indicate?

A
The system is unbound, and energy must be removed to separate the masses to infinity.
B
The system is gravitationally bound, and energy must be added to separate the masses to infinity.
C
The masses repel one another, so their potential energy is negative.
D
The potential energy is negative only when the masses are moving.

True or false

1 point

In a circular orbit, gravity provides the inward centripetal acceleration, and a separate centripetal force must also act on the object.

A
True
B
False

Choose all

1 point

Which statements describe Kepler’s law of areas? Select all that apply.

A
The line from the central body to the orbiting object sweeps out equal areas in equal times.
B
The object moves at constant speed throughout every elliptical orbit.
C
The object moves faster when closer to the central body and slower when farther away.
D
The line from the central body sweeps out greater areas during equal time intervals when the object is farther away.

Fill in the blank

1 point

According to Kepler’s law of areas, the line from a central body to an orbiting object sweeps out in equal times.

Choose one

1 point

A mass $m$ is in a circular orbit of radius $r$ around a much more massive body of mass $M$ . Which expression gives its total mechanical energy?

A
$E=\frac{GMm}{2r}$
B
$E=0$
C
$E=-\frac{GMm}{2r}$
D
$E=-\frac{GMm}{r}$

Written response

1 point

In Kepler’s law of orbits, at which geometric point of an elliptical orbit is the central body located?

Choose all

1 point

Which statements about gravitational forces are correct? Select all that apply.

A
Each body exerts an equal and opposite gravitational force on the other.
B
The gravitational force between two masses is always repulsive.
C
Forces from multiple bodies must be added as ordinary scalars, regardless of direction.
D
When several bodies contribute, their gravitational forces add as vectors.

Open ended

1 point

Explain why $\Delta U\approx mgh$ can be used for a small height change near Earth’s surface, and contrast it with the expression for gravitational potential energy of a mass at distance $r$ from an isolated mass.

Choose one

1 point

An orbiting object moves around the same much more massive central body, and its elliptical orbit’s semimajor axis doubles. By what factor does its orbital period change?

A
The period is multiplied by $2$ .
B
The period is multiplied by $2\sqrt{2}$ .
C
The period is multiplied by $4$ .
D
The period is divided by $2\sqrt{2}$ .

Written response

1 point

One mass in a two-body system is doubled while the other mass stays fixed, and the distance between their centers is tripled. What is the ratio of the new gravitational force to the original force?

Choose one

1 point

Two objects' masses remain unchanged while their center-to-center separation increases from $r$ to $3r$ . What happens to the magnitude of the gravitational force between them?

A
$\frac{1}{3}$ of its original value
B
$\frac{1}{9}$ of its original value
C
$3$ times its original value
D
$9$ times its original value

Choose one

1 point

At a point outside a spherical mass, what is the direction of the gravitational field?

A
Toward the central mass
B
Away from the central mass
C
Perpendicular to the line from the mass
D
In the same direction regardless of position

Choose one

1 point

An object follows an elliptical orbit around a central body. Where is the central body located relative to the ellipse?

A
At the ellipse's geometric center
B
At the orbiting object's starting point
C
At one focus of the ellipse
D
Outside the plane of the ellipse

Choose one

1 point

Two objects orbit the same much more massive body in ideal circular orbits with the same radius. How do their orbital speeds compare if one object has twice the mass of the other?

A
The heavier object has twice the speed
B
The lighter object has twice the speed
C
The heavier object has half the speed
D
Both objects have the same speed

Choose one

1 point

A mass has gravitational potential energy $-96\ \mathrm{J}$ at distance $r$ from an isolated spherical body, with zero potential energy at infinity. What is its potential energy at distance $3r$ ?

A
$-32\ \mathrm{J}$
B
$-288\ \mathrm{J}$
C
$32\ \mathrm{J}$
D
$-96\ \mathrm{J}$

Written response

1 point

Near Earth's surface, an object of mass $2.5\ \mathrm{kg}$ is in a gravitational field of magnitude $9.8\ \mathrm{m/s^2}$ . What is the magnitude of the gravitational force on it?