Thursday, March 26, 2009

Newton's 3rd Law Not Valid!

As u know, IIIrd law of motion says that for every action(force), there is equal and opposite reaction.

Now let us understand how and when Newton's IIIrd Law can be voilated:

Suppose two bodies "A" and "B" come in contact with each other.
In that case, the contact will lead to transfer of force from A to B (or vice versa).

Now, there is a subtle point here. Every force takes some time to get transmitted. So, if 
by any chance, A and B remain in contact with each other for a time which is less than 
the time for the force to get transmitted between A and B, it essentially means there is 
no reaction, though both the bodies came in contact with each other.

This is a violation of Newton;s IIIrd law of motion..

For details, please see Berkeleys Physics book.


  1. if the time is less than the time for the force to get transmitted (your words), why SHOULD there be a reaction? there isn't any force "transmitted" so there shouldn't be any reaction and there indeed is none.

    that is but one of your errors.

  2. While Newton's 3rd law can be violated, the description of the example does not show it.