According to Newton's 3rd law, $ F_{A\to B} = -F_{B\to A} $, when you apply a force to an object, it applies the same force (against you?).

When I stretch a strap with my hands, which force exactly is it generating in return?


  • $\begingroup$ Are you referring to the deformational behavior of elastomeric solids? $\endgroup$ – Chet Miller Nov 22 at 21:38

Your left forefinger is exerting a force on one end of the band. Your right forefinger is exerting a force on the other end. Each end of the band is exerting a force on the finger with which it is in contact. You can see this, because the ends of your forefingers have turned white and have temporary grooves in them!

[Try not to suppose that the band is 'reacting' to the forces that you are applying. The force that you apply to one end of the band and the force that that end applies to you are part of a symmetrical interaction; it's not a case of cause and effect.]

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  • $\begingroup$ "not a case of cause and effect." Bravo! $\endgroup$ – Bill N Nov 21 at 19:22
  • $\begingroup$ Thanks to clear it out! So obvious when I actually read it.. :) $\endgroup$ – Ben Nov 23 at 10:28

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