Back To Course

ORELA General Science: Practice & Study Guide62 chapters | 577 lessons

Watch short & fun videos
**
Start Your Free Trial Today
**

Start Your Free Trial To Continue Watching

As a member, you'll also get unlimited access to over 70,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.

Free 5-day trial
Your next lesson will play in
10 seconds

Lesson Transcript

Instructor:
*David Wood*

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

You probably have an idea of what gravity is, but did you know that you, right now, are actually pulling on every other object in the universe? Find out more about the gravitational force and learn an equation to calculate its pull on other objects.

The universe has a lot of forces, a lot of pushes and pulls. We're always pushing or pulling something, even if only the ground. But it turns out that in physics, there are really only four fundamental forces from which everything else is derived: the strong force, the weak force, the electromagnetic force, and the gravitational force.

The **gravitational force** is a force that attracts any two objects with mass. We call the gravitational force *attractive* because it always tries to pull masses together, it never pushes them apart. In fact, every object, including you, is pulling on every other object in the entire universe! This is called Newton's **Universal Law of Gravitation**. Admittedly, you don't have a very large mass and so, you're not pulling on those other objects much. And objects that are really far apart from each other don't pull on each other noticeably either. But the force is there and we can calculate it.

This equation describes the force between any two objects in the universe:

In the equation:

*F*is the force of gravity (measured in Newtons, N)*G*is the gravitational constant of the universe and is always the same number*M*is the mass of one object (measured in kilograms, kg)*m*is the mass of the other object (measured in kilograms, kg)*r*is the distance those objects are apart (measured in meters, m)

So if you know how massive two objects are and how far they are apart, you can figure out the force between them.

Notice that the distance (*r*) on the bottom of the equation is squared. This makes it an inverse square law. Because of this, if you double the distance between two objects, you reduce the gravitational force between them to a quarter of what it was. Or if you triple the distance between them, you reduce the force to a ninth of what it was. Or if we go the other way, halving the distance between two objects multiplies the force by a factor of four. This can be used to make rough comparisons between situations.

Let's go through an example of how to use the equation. Let's try to calculate the force between an adorable baby and the planet Mars!

Let's say the baby weighs 4.5 kg and the planet Mars has a mass of 6.4x10^23. The distance between Earth and Mars changes, but it's an average of 2.25x10^11 meters. And as usual, G is 6.67 x 10^-11. All we have to do is plug those numbers in and solve for *F*:

And that gives us 3.8 x 10^-9 Newtons. This is a tiny force, partly because a baby has such a small mass and partly because they're so far apart.

The **gravitational force** is a force that attracts any objects with mass. You, right now, are pulling on every other object in the entire universe! This is called Newton's **Universal Law of Gravitation**. We can use the equation shared in this lesson to calculate the force between any two objects, as long as we know their masses and how far apart they are. We can also compare two situations by realizing that gravity is an inverse-square law, meaning that if you double the distance between two objects, you reduce the force to a quarter. And if you triple the distance between two objects, you reduce the force to a ninth.

When you are finished, you should be able to:

- State the Universal Law of Gravitation
- Write the equation to calculate gravitational force and state the meaning of its variables
- Explain how gravity is an inverse-square law

To unlock this lesson you must be a Study.com Member.

Create
your account

Already a member? Log In

BackDid you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

You are viewing lesson
Lesson
9 in chapter 21 of the course:

Back To Course

ORELA General Science: Practice & Study Guide62 chapters | 577 lessons

- Newton's First Law of Motion: Examples of the Effect of Force on Motion 8:25
- Mass and Weight: Differences and Calculations 5:44
- Free-Body Diagrams 4:34
- Newton's Second Law of Motion: The Relationship Between Force and Acceleration 8:04
- Newton's Third Law of Motion: Examples of the Relationship Between Two Forces 4:24
- Newton's Laws and Weight, Mass & Gravity 8:14
- The Acceleration of Gravity: Definition & Formula 6:06
- Determining the Acceleration of an Object 8:35
- Gravitational Force: Definition, Equation & Examples 3:40
- Go to ORELA General Science: Newton's Laws & Gravity

- Psychology 315: Psychology of Motivation
- Fraud Examination: Help & Review
- Psychology 314: Psychology of Learning
- Computer Science 201: Data Structures & Algorithms
- Drama 101: Intro to Dramatic Art
- Studying for Philosophy 101
- Motivation & Neuroscience
- Core Data Structures
- Object-Oriented Design Fundamentals
- Analyzing Algorithms
- Study.com FTCE Scholarship: Application Form & Information
- Study.com CLEP Scholarship: Application Form & Information
- List of FTCE Tests
- CLEP Prep Product Comparison
- CLEP Exam vs. AP Test: Difficulty & Differences
- CLEP Tests for the Military
- How to Transfer CLEP Credits

- Dollar Diplomacy: Definition & Examples
- Radio Wave: Definition, Spectrum & Uses
- SQL TRUNCATE String: Tutorial & Overview
- Business Analysis Tools, Techniques & Software
- Interpreting Pulmonary Diagnostics: Normal vs. Abnormal Results
- Health Policy Resources: Financial & Administrative
- Managing Relationships with Employees
- Edward Gibbon's Contributions to History & Historiography
- Quiz & Worksheet - Low Self-Esteem & Bullying
- Quiz & Worksheet - Demand Forecasting Techniques
- Quiz & Worksheet - How to Use Historical Data
- Quiz & Worksheet - Systems Thinking & Environmental Ethics
- Quiz & Worksheet - 4 Sided Polygons
- Political Philosophy & Social Justice Flashcards
- Ethics in Philosophy Flashcards

- NYSTCE Chemistry: Practice and Study Guide
- AEPA Middle Grades Social Science: Practice & Study Guide
- AP Physics C: Homeschool Curriculum
- UExcel Contemporary Mathematics: Study Guide & Test Prep
- Microbiology for Teachers: Professional Development
- NMTA Social Science: Political Developments (1760-1848)
- OAE - Integrated Science: Magnetism
- Quiz & Worksheet - Types of Circumstantial Evidence
- Quiz & Worksheet - Characteristics of Comparative Form
- Quiz & Worksheet - SAT Questions on Standard English Conventions
- Quiz & Worksheet - Characteristics & Analysis of Categorical Data
- Quiz & Worksheet - Converting mph to m/s

- Alliterative Verse: Definition & Examples
- Lew Wallace: Biography & Books
- Trench Warfare Lesson Plan
- What is Saxon Math?
- Science Project Grading Rubrics
- How to Pass Calculus
- Communism Lesson Plan
- Writing Center Resources
- What is the TACHS Exam?
- How to Pass the CPA Exam
- Florida Teacher Certification Renewal
- English Conversation Topics

Browse by subject