Question 1

Which of the following best describes the concept of a gravitational field as developed for electromagnetic interactions?

Accepted Answer

A region in space where mass creates a field that permeates all space, and other masses experience a force when entering it.

Question 2

What is the correct formula for the gravitational field strength $$g at a $$distance $$r$$ from a mass $$M$$?

Accepted Answer

$$g = \frac{GM}{r^2$}$$

Question 3

A satellite is placed into a circular orbit around Earth. Which force must be balanced to maintain this orbit?

Accepted Answer

The gravitational force must be balanced by the centripetal force.

Question 4

Given Earth's radius $$r_E = 6.38 	imes 10^6$ m, what is the correct expression for the velocity v$ of a satellite in a circular orbit just above Earth's surface?

Accepted Answer

$$v = \sqrt{\frac{GM_E}{r_E}}$$

Question 5

Which of the following statements about synchronous (geostationary) orbits is correct?

Accepted Answer

A satellite in synchronous orbit remains above the same point on Earth's surface.

Question 6

Kepler's First Law states that the path of each planet around the Sun is:

Accepted Answer

An ellipse with the Sun at one focus.

Question 7

According to Kepler's Second Law, what does the line joining a planet and the Sun do?

Accepted Answer

Sweeps out equal areas in equal periods of time.

Question 8

Kepler's Third Law relates the period $$T$$ and mean distance $$a of a $$planet from the Sun. Which equation correctly expresses this law?

Accepted Answer

$$\frac{T_1$^2}{T_2$^2} = \frac{a_1$^3}{a_2$^3}$$

Question 9

If Mars has a period of 687 Earth days and Earth's mean distance from the Sun is $$1.50 	imes 10$$^{11}$$ m, what is the ratio of the squares of their periods according to Kepler's Third Law?

Accepted Answer

$$\left(\frac{687}{365}\$$right)^2$$

Question 10

Newton’s Law of Universal Gravitation is given by which formula?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 11

A satellite in orbit is said to be 'constantly falling.' What prevents it from crashing into Earth?

Accepted Answer

Its tangential speed keeps it moving forward, so it continually misses the ground.

Question 12

Which of the following is NOT one of the four fundamental forces of nature?

Accepted Answer

Frictional force

Question 13

If the gravitational field strength at a distance $$r$$ from a planet of mass $$M is$$ $$g = \frac{GM}{r^2$}$$, what happens to $$g if $$the distance is doubled?

Accepted Answer

It becomes one-fourth as strong.

Question 14

A satellite is launched with a velocity greater than the required circular orbital velocity. What will happen to its trajectory?

Accepted Answer

It will move into an elliptical or escape trajectory, possibly leaving Earth's gravity.

Question 15

Which of the following best explains why Kepler’s laws are valid according to Newton’s law of gravitation?

Accepted Answer

Newton’s law provides the theoretical basis for the empirical laws observed by Kepler.

Question 16

If a planet’s orbit around the Sun is an ellipse, what is located at one of the foci?

Accepted Answer

The Sun

Question 17

Which equation correctly relates the centripetal acceleration $$a of a $$satellite in circular orbit to its velocity $$v$$ and orbital radius $$r$$?

Accepted Answer

$$a = \frac{v^2$}{r}$$

Question 18

A student claims that a satellite in orbit does not experience gravity. Which statement best corrects this misconception?

Accepted Answer

Satellites in orbit are constantly experiencing gravity, which provides the centripetal force for their motion.

Gravitation: Fields, Orbits, and Planetary Motion

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