Skip to ContentGo to accessibility page
OpenStax Logo
Physics

Short Answer

PhysicsShort Answer

Short Answer

7.1 Kepler's Laws of Planetary Motion

27 .
Explain how the masses of a satellite and its parent body must compare in order to apply Kepler’s laws of planetary motion.
  1. The mass of the parent body must be much less than that of the satellite.
  2. The mass of the parent body must be much greater than that of the satellite.
  3. The mass of the parent body must be equal to the mass of the satellite.
  4. There is no specific relationship between the masses for applying Kepler’s laws of planetary motion.
28 .
Hyperion is a moon of the planet Saturn. Its orbit has an eccentricity of 0.123 and a semi-major axis of 1.48 × 10 6 km . How far is the center of the orbit from the center of Saturn?
  1. 1.82 × 10 5 km
  2. 3.64 × 10 5 km
  3. 1.20 × 10 7 km
  4. 2.41 × 10 7 km
29 .
The orbits of satellites are elliptical. Define an ellipse.
  1. An ellipse is an open curve wherein the sum of the distance from the foci to any point on the curve is constant.
  2. An ellipse is a closed curve wherein the sum of the distance from the foci to any point on the curve is constant.
  3. An ellipse is an open curve wherein the distances from the two foci to any point on the curve are equal.
  4. An ellipse is a closed curve wherein the distances from the two foci to any point on the curve are equal.
30 .
The planet Mars has two moons, Deimos and Phobos. Deimos orbits Mars every 1.26 days with an average radius of 2.35 × 103 km. Phobos has an average orbit about four times greater in radius than Deimos. How long does it take for Phobos to make an orbit of Mars?
  1. 2.24 days
  2. 5.04 days
  3. 9.40 days
  4. 10.0 days

7.2 Newton's Law of Universal Gravitation and Einstein's Theory of General Relativity

31.

Newton’s third law of motion says that, for every action force, there is a reaction force equal in magnitude but that acts in the opposite direction. Apply this law to gravitational forces acting between the Washington Monument and Earth.

  1. The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with a force equal to Earth’s weight. The situation can be represented with two force vectors of unequal magnitude and pointing in the same direction.
  2. The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with a force equal to Earth’s weight. The situation can be represented with two force vectors of unequal magnitude but pointing in opposite directions.
  3. The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with an equal force. The situation can be represented with two force vectors of equal magnitude and pointing in the same direction.
  4. The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with an equal force. The situation can be represented with two force vectors of equal magnitude but pointing in opposite directions.
32.

True or false—Gravitational force is the attraction of the mass of one object to the mass of another. Light, either as a particle or a wave, has no rest mass. Despite this fact gravity bends a beam of light.

  1. True
  2. False
33 .
The average radius of Earth is 6.37 × 10 6 m . What is Earth’s mass?
  1. 9.35 × 10 17 kg
  2. 5.96 × 10 24 kg
  3. 3.79 × 10 31 kg
  4. 2.42 × 10 38 kg
34 .
What is the gravitational force between two 60.0 kg people sitting 100 m apart?
  1. 2.4 × 10 − 11 N
  2. 2.4 × 10 − 9 N
  3. 3.6 × 10 − 1 N
  4. 3.6 × 10 1 N
PreviousNext
Order a print copy
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute Texas Education Agency (TEA), and must distribute any derivative works under the same license. The original material is available at: https://www.texasgateway.org/book/tea-physics . Changes were made to the original material, including updates to art, structure, and other content updates.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Jul 8, 2026 Texas Education Agency (TEA). The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.