1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding the magnitude necessary to balance two forces

  1. Mar 20, 2014 #1
    1. The problem statement, all variables and given/known data
    Two forces are acting on an object. The magnitudes of them are F1=10.0N, F2=4.0N. If a third force F3 is applied on the object, what is the smallest magnitude of F3 needed to balance the first two forces?

    2. Relevant equations

    3. The attempt at a solution
    I've done a lot of internet searching for this question and had no luck. With that being said, I am really starting from ground zero here (hence no equation). I'm guessing that this problem has to do with FNET and is probably easier than it looks? If someone could give me an equation to use I would probably be in good shape. Thank you!
  2. jcsd
  3. Mar 20, 2014 #2
    Yes, it's very easy and you guessed the right equation. The word "balanced" can only mean the object is in equilibrium.
  4. Mar 20, 2014 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Try a graphical approach. For example choose arbitrary values, say F1 = 3 and F2 = 4 and draw a few vector sum diagrams to scale with F1 and F2 pointing in different directions such as...

    a) F2 and F1 pointing in the same direction
    b) F2 at 90 degrees to F1
    c) F2 at 45 degrees to F1
    d) F2 at 135 degrees to F1
    c) F2 in the opposite direction to F1

    In which direction must they point to give the smallest Fnet that F3 must oppose?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted