# Ch 5: Newton's Laws in Astronomy

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### About This Chapter

## Newton's Laws in Astronomy - Chapter Summary and Learning Objectives

Let instructors teaching this chapter demonstrate the physics at work in everything from the simplest action-reaction force pairs to the gravity and normal forces that keep us stable. You can also discover equations used to calculate mass, acceleration and other variables accounted for by Newton's laws of motion. Lessons in this chapter are designed to teach you how to do the following:

- List types of contact and non-contact forces
- Calculate the net force acting on an object
- Describe the relationship between weight, mass and gravity
- Calculate the acceleration of an object
- Interpret a free-body diagram

Video | Objectives |
---|---|

Newton's First Law of Motion: Examples of the Effect of Force on Motion | Use Newton's first law of motion to examine unbalanced and balanced forces, inertia and friction. |

Distinguishing Between Inertia and Mass | Learn how an object's mass affects its inertia. |

Mass and Weight: Differences and Calculations | Differentiate mass from weight. Get tips for using one variable to calculate the other. |

State of Motion and Velocity | Learn how to define the speed and velocity of an object in motion. Study the effects of circular motion on velocity. |

Force: Definition and Types | Get examples of contact forces, like friction, air resistance and applied force. Explore non-contact forces, such as gravity and magnetic force. |

Forces: Balanced and Unbalanced | Examine the static and dynamic equilibriums of objects with balanced forces. Learn how unbalanced forces cause an object's state of motion to change. |

Free-Body Diagrams | Discover the vector diagrams used to depict the magnitude and direction of forces acting on an object. |

Net Force: Definition and Calculations | Learn how to add or subtract forces acting on an object in order to determine the net force. |

Newton's Second Law of Motion: The Relationship Between Force and Acceleration | Apply Newton's second law of motion to describe how net force and mass can be used to calculate acceleration. |

Determining the Acceleration of an Object | Practice finding the acceleration of an object when given the change in velocity and the change in time. |

Determining the Individual Forces Acting Upon an Object | Get tips for determining whether such forces as gravity, normal force, friction or tension are acting on an object. |

Air Resistance and Free Fall | Examine the acceleration of objects in free fall. Describe the effect of air resistance and mass. |

Newton's Third Law of Motion: Examples of the Relationship Between Two Forces | Learn how action-reaction force pairs demonstrate Newton's third law of motion. |

Newton's Laws and Weight, Mass & Gravity | Study the effect of gravity on the acceleration and weight of falling objects. |

Identifying Action and Reaction Force Pairs | Identify the effect of an object's mass in action-reaction force pairs. |

The Normal Force: Definition and Examples | Examine how the force exerted by surfaces works with gravity to keep things in place. |

Friction: Definition and Types | Differentiate between static and sliding friction. |

### 1. Newton's First Law of Motion: Examples of the Effect of Force on Motion

This lesson describes Newton's first law of motion, also known as the law of inertia. The interaction between force and motion is explained. Several examples are used to discuss the implications of this law on earth and in space.

### 2. Newton's Second Law of Motion: The Relationship Between Force and Acceleration

This lesson defines Newton's second law of motion. Examples are used to illustrate how unbalanced forces cause objects to accelerate. The examples are used to practice calculating acceleration and force for objects in motion.

### 3. Newton's Third Law of Motion: Examples of the Relationship Between Two Forces

This lesson describes Newton's third law of motion. Examples are provided to illustrate how interacting objects experience forces. The lesson explains how objects accelerate as a result of force. Applications of Newton's third law are illustrated in nature, machines, and space.

### 4. Newton's Laws and Weight, Mass & Gravity

Did you know that mass and weight are not the same? This lesson describes the difference between the two as well as the effect of gravity on weight. Examples are used to teach you how to calculate weight based on mass and acceleration of gravity.

### 5. The Law of Universal Gravitation: Definition, Importance & Examples

Gravity is what pulls us toward Earth, but it's also what pulls Earth toward us. This is explained by the law of universal gravitation, which describes how all objects in the universe have this important force between them.

### 6. Newton's Law of Gravitation: Definition & Examples

This lesson explains how gravity works mathematically and teaches you how to use Newton's Law of Gravitation to solve problems. A short quiz will follow.

### 7. Force: Definition and Types

Force is everywhere and it comes in a variety of sizes, directions, and types. In this video lesson, you'll identify force as well the different types of force that objects may experience.

### 8. Work as an Integral

After watching this video, you will be able to solve calculus problems involving work and explain how that relates to the area under a force-displacement graph. A short quiz will follow.

### 9. Mass and Weight: Differences and Calculations

We often talk about mass and weight as if they are the same. While they are proportional to each other, they are not in fact the same. In this video lesson you will learn to distinguish between the two, as well as convert one to the other.

### 10. The Normal Force: Definition and Examples

You're likely pretty familiar with gravity because it holds you down to the surface of Earth. But in this lesson, you'll learn about the normal force, which also helps keep you on the surface of Earth.

### 11. Friction: Definition and Types

You experience friction all the time, and you should be glad you do! Friction helps keep stationary objects in place as well as slow moving objects down as they slide across a surface. This lesson identifies what friction is and explains the two ways we find this force on earth.

### 12. Forces: Balanced and Unbalanced

Forces are needed to start or stop an object's motion, but can also be involved when an object is at rest or already traveling at constant velocity. In this video lesson, you'll identify the difference between balanced and unbalanced forces, understanding how they affect the movement of objects.

### 13. Identifying Action and Reaction Force Pairs

Good things often come in pairs, and forces are no exception. In this lesson you'll explore Newton's second and third laws of motion to understand how action and reaction pairs affect objects interacting with each other.

### 14. Net Force: Definition and Calculations

Because forces are vectors, we can't simply add them up to get a total amount of force on an object. Instead, we calculate the net force, which is important to understand because it tells us about an object's state of motion.

### 15. Determining the Individual Forces Acting Upon an Object

Objects constantly have forces acting on them whether they are moving or at rest. In this video lesson, you'll understand how to identify the individual forces acting on an object by reviewing the different types of forces and the use of free-body diagrams.

### 16. Free-Body Diagrams

Forces that act on an object can be drawn through special vector diagrams called free-body diagrams. In this video lesson you'll identify how to correctly represent forces in a free-body diagram through vector arrows and force labels.

### 17. Distinguishing Between Inertia and Mass

Mass and inertia are both related to the amount of matter an object has, but they aren't exactly the same thing. In this video lesson, you'll see how mass affects an object's inertia, which in turn affects that object's motion.

### 18. State of Motion and Velocity

An object's state of motion describes how it is moving. But there are many ways we can describe motion, such as speed and velocity. This motion is relative to other objects around it, such as the earth, the sun, and even other stars in our galaxy.

### 19. Determining the Acceleration of an Object

Acceleration is a change in an object's state of motion. A few variables need to be identified to calculate an object's acceleration, but once we have those values, we can put them into a simple equation to find out how quickly or slowly an object's velocity is changing.

### 20. Air Resistance and Free Fall

Through experiments by Galileo and Newton, we can understand why all objects in free-fall experience the same acceleration, ''g''. We can also see why air resistance affects a falling object's velocity and how this can lead to a falling object reaching a terminal velocity.

### 21. Gravitational Potential Energy: Definition, Formula & Examples

In this lesson, you will learn what gravitational potential is, the equation we use to calculate it, and how to use that equation. We'll look at some real life examples so you can see how it works. A short quiz will follow.

### 22. Gravitational Attraction of Extended Bodies

After watching this lesson, you will be able to explain what an extended body is, understand the derivation for the force of gravity between a point charge and a long, thin bar and solve problems using the result of that derivation.

### 23. The Acceleration of Gravity: Definition & Formula

In this lesson, we will introduce the acceleration due to gravity. Objects in free fall are one of the few real world examples of straight line motion with constant acceleration, so they are commonly used when learning kinematics.

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### Other Chapters

Other chapters within the Astronomy 101: Intro to Astronomy course

- The History of Astronomy
- How Scientists Think and Work
- Matter in Astronomy
- Light in Astronomy
- Momentum, Energy, Pressure, Temperature & Gas
- Rotational Motion in Physics
- Earth's Spheres and Astronomy
- Influences on Climate
- The Orbits of Celestial Bodies
- The Earth, Sky, and Moon
- The Moon: Formation & Phases
- The Atmosphere on Earth and Other Planets
- The Sun's Structure & Components
- The Solar System: Layout, Formation & Dating
- Characteristics of Our Solar System's Planets
- Small Celestial Bodies & Satellites in Our Solar System
- Measurement of Star Qualities
- Star Types and Significance
- The Birth and Life of Stars
- Star Death and Stellar Remnants
- The Milky Way Galaxy
- Galaxies: Properties & Characteristics
- The Universe: Key Concepts & Theories
- Life in the Universe
- Celestial Navigation & Timekeeping
- Relativity in Time and Space
- Telescopes