Why is There Acceleration Despite Newton's Third Law of Motion?

  • Thread starter AllenHe
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In summary, Newton's 3rd law states that for every force exerted by one body on another, there is an equal and opposite force exerted by the second body on the first. This means that if two objects are pushing against each other with equal force, they will not move. However, if there are other forces acting on the objects, then there may be acceleration. Newton's 2nd law states that to find the acceleration of a particular object, one must consider the forces acting on that specific object.
  • #1
AllenHe
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Homework Statement


The law states that "Whenever one body exerts a force on another, the second exerts an equal and opposite force on first." But then, why is there acceleration?


Homework Equations





The Attempt at a Solution


If there will be force responding to the first one with equal magnitude, then there won't be any net force.Then why is there acceleration?
 
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  • #2
One must keep in mind that the two forces mentioned in Newton's 3rd law act on two different bodies.
 
  • #3
but, for example. When I push a wall, I will exert a force on the wall, and the wall will exert a force on me.
In another case, when I am pushing a person with 100N, and that person also pushes me with 100N, in opposite direction, then none of us will move. How do you explain that?
 
  • #4
Consider a person being pushed by me by 100N.
To find whether he will accelerate or not one has to see if there are other forces acting thus contributing to increase or decrease the effect of the !00N that I am applying.
That is to find HIS acceleration one is interested in the forces acting ON HIM and not on me.
 
  • #5
Oh, so what you are saying is that it's other forces which make the person accelerate, right?
 
  • #6
What I said was that to find the acceleration on a certain mass, one has to find the forces acting on THAT mass. That is what Newton's 2nd law says.
 

1. What is Newton's third law of motion?

Newton's third law of motion 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 will exert an equal force in the opposite direction.

2. How does Newton's third law apply to everyday life?

Newton's third law can be seen in everyday life in many ways. For example, when you walk, your feet push against the ground and the ground pushes back with an equal force, allowing you to move forward. Another example is when you sit on a chair, your weight pushes down on the chair and the chair pushes back with an equal force, keeping you balanced and in place.

3. Can Newton's third law be violated?

No, Newton's third law is a fundamental law of nature and cannot be violated. In every interaction, forces are always exchanged in pairs, and the magnitude of the forces will always be equal and opposite.

4. How does Newton's third law relate to momentum?

Newton's third law is closely related to momentum, as momentum is defined as the product of an object's mass and velocity. According to Newton's third law, when objects interact, the forces they exert on each other are equal and opposite, but their respective momentums will also be equal and opposite. This means that the total momentum of a system will remain the same, unless acted upon by an external force.

5. What is the significance of Newton's third law in physics?

Newton's third law is an important principle in physics as it helps explain how objects interact with each other and how forces work in the natural world. It is also essential in understanding concepts such as conservation of momentum and how objects can move and accelerate. Without this law, many phenomena in the world would not be explainable.

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