Can you please help me with Newtons 3rd Law

  1. how do you find the Tension force,acceleration,magnitude.
    Its those questions where you have pullys,boxes pushing each other...
    I am really confused for the 3rd law
     
  2. jcsd
  3. Do you have a specific example? I'd hate to just vapidly repeat the definition of the 3rd law, which you can easily find anywhere and everywhere....
     
  4. Two masses are places in a frictionless pulley system.Solve for the acceleration and tension forces.
    1st box is 4kg and the other is 3kg

    well i know,
    fnet=ma
    fg=mg
    ff=muFn
     
  5. sophiecentaur

    sophiecentaur 13,278
    Science Advisor
    Gold Member

    You could start by saying that there is a net, unbalanced force of 10N (For GCSE level thought - or you can do 9.81m/s/s, if you like), pulling one up and one down.
    This is accelerating both the masses (7kg total), use your formula to find the acceleration.
    The tension will be ml times (g + this acceleration) for the light mass and also mh times (g- this acceleration) for the heavy mass. Those two values should be the same, natch - as a check.
    etc etc - you can put in the numbers
     
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