Understanding Newton's Third Law of Motion: A Law of Forces Explained

In summary, Newton's first two laws of motion focus on the persistence of velocity and the relationship between net forces and acceleration. However, the third law is more about the nature of forces and their equal and opposite pairs. This can be seen in the fact that the third law is often referred to as a law of forces, just like the superposition of forces. While some may argue that this disconnects forces from motion, it is important to consider that forces and motion are closely intertwined. This is why a more accurate statement of Newton's third law includes references to bodies, rather than just forces. Additionally, while the superposition of forces is a principle used in the first two laws, it is not explicitly stated as a law of motion.
  • #1
Dschumanji
153
1
It is clear that Newton's first two laws of motion deal with motion: the velocity of a moving body is persistant, and net forces cause acceleration of such a body. However, in my opinion, the third law has more to do with the nature of forces rather than motion. The main point is that forces come in pairs of equal magnitude but opposite direction.

Newton's third law of motion should be considered a law of forces, such as the superposition of forces is a law of forces.

Any thoughts on this idea? Am I just being crazy?
 
Physics news on Phys.org
  • #2
Well a force is often associated with motion isn't it? The problem with considering it as a matter of force alone, is that it seems rather disconnected; if body A exerts force F on body B it itself experiences F in an opposite direction. You can't talk about forces alone without considering the bodies and their subsequent motion induced by the forces. Which is why a more accurate statement of Newton's third law makes references to bodies and not just forces.
 
  • #3
Defennder said:
Well a force is often associated with motion isn't it? The problem with considering it as a matter of force alone, is that it seems rather disconnected; if body A exerts force F on body B it itself experiences F in an opposite direction. You can't talk about forces alone without considering the bodies and their subsequent motion induced by the forces. Which is why a more accurate statement of Newton's third law makes references to bodies and not just forces.

So why isn't the superposition of forces itself considered a law of motion?
 
  • #4
I thought that was covered in Newton's 1st and 2nd law, which makes references to a "net" force.
 
  • #5
Defennder said:
I thought that was covered in Newton's 1st and 2nd law, which makes references to a "net" force.
It makes use of the principle but is not covered in the first or second law.
 
  • #6
It is given in the statement of the first two laws. The laws use the word "net" which is essentially the superposition principle.
 

What is Newton's Third Law of Motion?

Newton's Third Law of Motion, also known as the Law of Action and Reaction, states that for every action, there is an equal and opposite reaction. This means that when an object exerts a force on another object, the second object exerts an equal and opposite force on the first object.

How does Newton's Third Law of Motion apply to everyday life?

Newton's Third Law of Motion can be seen in various aspects of everyday life. For example, when you walk, your feet push against the ground, and the ground pushes back with an equal and opposite force, allowing you to move forward. Similarly, when you sit on a chair, your weight exerts a downward force on the chair, and the chair exerts an equal and opposite upward force on you, keeping you in place.

Are there any exceptions to Newton's Third Law of Motion?

No, there are no exceptions to Newton's Third Law of Motion. This law applies to all objects and all types of forces, whether they are contact forces (e.g. pushing, pulling) or non-contact forces (e.g. gravity, electromagnetism).

How is Newton's Third Law of Motion related to the conservation of momentum?

Newton's Third Law of Motion is closely related to the conservation of momentum, which states that the total momentum of a system remains constant unless acted upon by an external force. In other words, the momentum gained by one object due to an action force is equal to the momentum lost by the other object due to the reaction force, thus maintaining the overall momentum of the system.

Can Newton's Third Law of Motion be applied to non-physical systems?

Yes, Newton's Third Law of Motion can be applied to non-physical systems, such as economics or social interactions. In these systems, the forces are not physical, but they still follow the principle of action and reaction. For example, when a country imposes a trade tariff on another country, the second country may retaliate with an equal and opposite tariff, resulting in an overall zero-sum gain.

Similar threads

Replies
35
Views
3K
Replies
23
Views
3K
Replies
27
Views
1K
Replies
8
Views
240
  • Mechanics
Replies
18
Views
1K
Replies
117
Views
6K
  • Mechanics
Replies
1
Views
735
  • Mechanics
Replies
4
Views
600
Replies
66
Views
8K
Back
Top