What are Newton's 1st and 3rd Laws?

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Newton's **First** and **Third Laws of Motion** are fundamental principles that describe the relationship between the motion of an object and the forces acting upon it. They were formulated by Sir Isaac Newton in his seminal work *Philosophiæ Naturalis Principia Mathematica* published in 1687. Here's a detailed explanation of each:

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### **Newton's First Law of Motion: The Law of Inertia**

**Statement:**
*An object at rest will remain at rest, and an object in motion will continue to move at a constant velocity in a straight line unless acted upon by an external force.*

**Explanation:**
- **Inertia:** This law introduces the concept of inertia, which is the tendency of objects to resist changes in their state of motion. 
- **Implications:**
  - **At Rest:** If an object is not moving, it won't start moving unless a force causes it to.
  - **In Motion:** If an object is moving, it won't stop or change direction unless a force acts upon it.
  
**Examples:**
- **Seatbelts in Cars:** When a car suddenly stops, passengers tend to lurch forward. Seatbelts provide the external force needed to change their state of motion, preventing injury.
- **Books on a Table:** A book will remain at rest on a table until someone applies a force to move it.
- **Spacecraft in Space:** In the vacuum of space, without external forces like gravity or propulsion, a spacecraft will continue moving indefinitely at a constant speed and direction.

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### **Newton's Third Law of Motion: The Action-Reaction Principle**

**Statement:**
*For every action, there is an equal and opposite reaction.*

**Explanation:**
- **Action and Reaction Forces:** When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
- **Mutual Forces:** These forces are always in pairs and act on different objects.
  
**Examples:**
- **Walking:** When you walk, your foot pushes backward against the ground (action), and the ground pushes your foot forward with an equal and opposite force (reaction), propelling you forward.
- **Rocket Propulsion:** Rockets expel gas molecules downward at high speed (action), and the reaction force pushes the rocket upward.
- **Swimming:** A swimmer pushes water backward with their hands and feet (action), and the water pushes the swimmer forward (reaction).

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### **Key Points to Remember**

- **Distinct from Second Law:** While Newton's Second Law relates force, mass, and acceleration (*F = ma*), the First and Third Laws focus on the behavior of objects in response to forces.
- **Action and Reaction Forces Do Not Cancel Each Other:** They act on different objects, so they don't negate each other but instead affect each object's motion individually.
- **Inertia Requires Overcoming:** To change an object's motion (its velocity), a net external force must overcome its inertia as described by the First Law.

Understanding Newton's First and Third Laws provides a foundational framework for analyzing motion and forces in classical mechanics, enabling us to comprehend everything from everyday activities to complex engineering systems.
Newton's **First Law** states that an object at rest stays at rest and an object in motion stays in motion unless a force acts on it. This is about inertia. Newton's **Third Law** says that for every action, there's an equal and opposite reaction. When one object pushes another, the second object pushes back with the same force in the opposite direction. These laws help explain how objects move and respond to forces.

What are Newton’s 1st and 3rd Laws?

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