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If a magnet exerts force on a iron block (opposite and EQUAL), does a iron block also exerts force on magnet (via Newton's third law)? If yes then what magnetic property does it has to produce equal and opposite force on magnet considering that its not a ideal environment? If no then is it not the violation of newton's third law?

Qmechanic
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jaskaran
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    The answer to the first question is "yes". I do not understand what your second question means: Why do you think some kind of "ideal environment" is required? What is a "magnetic property"? – ACuriousMind Jul 15 '14 at 10:56
  • @jaskaran: Good question. I think the answer needs the knowledge of particle physics, electromagnetism and relativity. – Sensebe Jul 15 '14 at 14:10
  • My second question is that is that why does the iron produce magnetic field equal and opposite to the field produced by magnet....it takes quiet alot time for iron to get magnetized and produce field and that too is not equal, while i experimented and reach to conclusion that its equal... pls explain – jaskaran Jul 15 '14 at 16:23
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    Take a look at this similar post: http://physics.stackexchange.com/q/114466/ – Benjamin Mar 18 '16 at 21:49

2 Answers2

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It's not a violation of the Newtons law. (As AcuriousMind answers on the comments)

It's the very same magnetic force which prevents one solid the penetrate another solid. The only difference is that this force is weaker and works only over very small distance. If you have a iron block and a rubber pushed to gether ie. by gravity. Doesn't the Iron block have more force similarly as the magnet? No, the both produce the same force, but in the rubber, there is just more deformation needed to produce this same force. Even the pulling force works; ie. with cold welding you can produce a similar connection like the two magnets has. Principally it's the very same. The magnetic fields get too close each others, and so they get connected. If this magnetic force becomes the weak enough, the solid becomes a fluid, and this penetration becomes possible.

Is this then a violation of the newtons 3rd law?

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.

At least the fluid dynamics can't be derived from the newtons laws according to the mainstream physics. And you definetly become problem simply by defining the "body" of the fluid and how the forces are exerted. (I see this possible, and this idea even fits to the QED.)

This can been put more simple; even in fluids it's not a violation of newtons laws, the hydrostatic pressure is clear implication for this force. And if this force is missing in some direction, then the flow accelerates until there is no pressure left. Exactly as said by the Newton's first law. This video might provide the best explanation to your question; Feynman, Fun to Imagine 4, Magnets

Jokela
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Its a violation of Newton third law..because Newton third law only valid when 1)same kind of force ie when there is force of same nature So electromagnetic and block forces are not of same nature so Newton third will not hold

DINESH Beniwal
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