Confusion in Newton's 3rd law of motion

In summary: These two forces are both internal to the system of book + table, and they do not affect the motion of either the book or the table.In summary, the third law of motion states that action and reaction forces do not create equilibrium as they act upon two different bodies. In order to make a body move, the net force acting upon it must be considered, rather than the force exerted by it on another body. This can be understood through examples such as the horse and cart problem and the boat and passenger problem. However, when it comes to a book resting on a table, both the book and the table are in equilibrium because the forces acting on them cancel each other out. While the book exerts a force on the table,
  • #1
Shafia Zahin
31
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I'm having a lot of confusions in the 3rd law of motion.It says action and reaction forces do not create equilibrium as the forces act upon two different bodies.Okay,I understand that if I want to make a body move I'll have to count the net force that is acting upon it not the force that is being exerted by it on another body.I can understand it when I see the example of the horse and cart problem or the boat and passenger problem that the passenger exerts a force on the boat and that's why the boat move though the boat exerts an equal force to the passenger that doesn't make any effect on the boat's movement. But, I get confused when I see the example of a book resting on a table.If the book exerting a force on the table then the table should break or move because the table is also exerting an equal force on the book but the book is a different object.How can it create an equilibrium then?I mean, I can't match the two of the examples and getting more and more confused.
Please help me.
With regards,
Shafia.
 
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  • #2
Shafia Zahin said:
But, I get confused when I see the example of a book resting on a table.If the book exerting a force on the table then the table should break or move because the table is also exerting an equal force on the book but the book is a different object.How can it create an equilibrium then?
The book is in equilibrium because the net force on it is zero: The force of gravity (the earth) pulling down is canceled by the force of the table pushing up.

The table is also in equilibrium: The force that the book exerts on the table plus the weight of the table is balanced by the upward force that the ground exerts on the table.

It's true that the force that the book exerts on the table is equal and opposite to the force that the table exerts on the book. But so what?
 
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FAQ: Confusion in Newton's 3rd law of motion

What is Newton's 3rd law of motion?

Newton's 3rd law of motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal force in the opposite direction on the first object.

How does confusion arise in Newton's 3rd law of motion?

Confusion can arise in Newton's 3rd law of motion because people often incorrectly interpret the word "equal" to mean "balanced." This leads to the misconception that the forces acting on two objects must be equal in order for the law to apply. In reality, the forces only need to have the same magnitude and opposite direction.

Can Newton's 3rd law of motion be violated?

No, Newton's 3rd law of motion is a fundamental law of physics and cannot be violated. However, it may seem like it is being violated in certain situations, such as when one object appears to be moving without any apparent external force acting on it. This can be explained by the presence of internal forces within the object.

Does Newton's 3rd law of motion apply to all forces?

Yes, Newton's 3rd law of motion applies to all forces in the universe, including gravitational, electromagnetic, and nuclear forces. It is a universal law that governs the interactions between all objects.

How can we observe Newton's 3rd law of motion in everyday life?

We can observe Newton's 3rd law of motion in everyday life through various examples, such as a person pushing against a wall and feeling the wall push back, a rocket launching into space as the gases from the engine are expelled in the opposite direction, or a person jumping off a boat and seeing the boat move in the opposite direction.

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