Newton's III Law :- Help me Understand

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In summary, Newton's third law states that the force between two objects is equal and opposite. Depending on the situation, this law can be used to explain why objects don't move when they are pushed against each other or why objects move in a specific direction.
  • #1
Mo
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Hello all, need a little bit of help understanding Newton's third Law.

It states that:

" While body A exerts a force on body B, body B exerts an equal and opposite force on body A"

Okay, i can understand that.I also understand that the force are acting upon different bodies.

so (and here's the question..) if i push my desklamp across the .. desk.. then i am exerting a force in one direction on the lamp, and it is exerting an equal and opposite force on my hand.

If so, why can i still get the desklamp to move. In my textbook it tells me that the forces do not cancel each other out, because they act on different bodies, but .. still ... i obviously don't understand it all that well.

Okay the next question from the book was

Explain why forces occur only in pairs"

Is it simply enough to say: Whenever one body exerts a force on a second body, the second body always eerts a force on the first body, hence forces occur only in pairs.

Help + Advice please!

Regards,
Mo
 
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  • #2
Mo said:
Hello all, need a little bit of help understanding Newton's third Law.

It states that:

" While body A exerts a force on body B, body B exerts an equal and opposite force on body A"

Okay, i can understand that.I also understand that the force are acting upon different bodies.

so (and here's the question..) if i push my desklamp across the .. desk.. then i am exerting a force in one direction on the lamp, and it is exerting an equal and opposite force on my hand.

If so, why can i still get the desklamp to move. In my textbook it tells me that the forces do not cancel each other out, because they act on different bodies, but .. still ... i obviously don't understand it all that well.

The 3 laws of Newton do not act independent of each other.U'll have to use them at the same time.The answer to your 'dilemma' is that,according to the second law,to each force corresponds an acceleration.In your case,the hand that pushes the lamp gives it an acceleration equal to the ratio between the force and the lamps mass.The total force acting on the lamp is just the force u're using to push it along the table.Of course,nthere's the friction force,too,but that,if the coefficent is small,doesn't alter the results significantly.

Daniel.
 
  • #3
Thanks for your reply, but I am still not 100% , am i right in saying that the reason that my hand never acclerated off in the opposite direction (after all the lamp is exerting a force on my hand in the opposite direction) is because of the ratio between force and mass (making it a very small acceleration?)
 
  • #4
Mo said:
Thanks for your reply, but I am still not 100% , am i right in saying that the reason that my hand never acclerated off in the opposite direction (after all the lamp is exerting a force on my hand in the opposite direction) is because of the ratio between force and mass (making it a very small acceleration?)

It's not only your hand,yer whole body should be accelerating in the opposite direction with a tiny acceleration (due to the big ratio of masses:yours & the lamps).You don't move,becuase of the friction between your feet and and the floor,or between your butt and the chair your butt uses to relax...

Daniel.
 
  • #5
Thanks for your help :)

Regards.
Mo
 

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 one object exerts a force on another object, the second object will exert an equal force in the opposite direction on the first object.

2. Can you provide an example of Newton's Third Law?

Yes, a classic example of Newton's Third Law is when you push against a wall. According to the law, the wall will push back against you with an equal force. Another example is when you sit on a chair - your body exerts a downward force on the chair, and the chair exerts an equal and opposite force upwards on your body.

3. How does Newton's Third Law apply to everyday life?

Newton's Third Law applies to everyday life in many ways. For example, when you walk, your foot exerts a force on the ground, and the ground exerts an equal and opposite force on your foot, propelling you forward. Similarly, when you swim, your arms push against the water, and the water pushes back against your arms, propelling you through the water.

4. Is Newton's Third Law always true?

Yes, Newton's Third Law is always true in the sense that every action has an equal and opposite reaction. However, it is important to note that the two forces do not always have the same effect on the objects involved. For example, if you push on a wall with your hand, your hand will feel the force of the wall pushing back, but the wall itself will not move due to its larger mass.

5. How is Newton's Third Law related to the other laws of motion?

Newton's Third Law is related to the other laws of motion in the sense that it explains the interaction between two objects. Newton's First Law (inertia) states that objects will remain at rest or in motion unless acted upon by an external force. Newton's Second Law (F=ma) explains how forces cause changes in an object's motion. Newton's Third Law complements these laws by stating that every force has an equal and opposite reaction, and together, they provide a complete understanding of how objects move and interact.

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