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Homework Help: Vectors, concept question

  1. Oct 9, 2007 #1
    Two forces, of magnitude 4 N and 10 N, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object __________.
    can anyone please explain to me why the net force can be 10 N ?? thanks in advance.
  2. jcsd
  3. Oct 9, 2007 #2
    Net force can be 10 N because of the angles at which the forces are applied.

    You can see because of the values 4 and 10 that the net force cannot be more than 14.

    Secondly, the net force of 14 can only be achieved if the forces are working together at the SAME angle. If the angle difference is little off the net result will decrease because they begin to work against each other slightly.
    try on your calculator.

    4<130deg+10<30deg that is about ten at 52 degrees.
    then try 4<130deg+10<130deg
    then try 4<130deg+10<120deg

    do you know how to resolve vectors into their x y components?
  4. Oct 9, 2007 #3
    i know that the net force cannot be more than 14 . my question was how do we get resultant vector to be 10N. do i know how to resolve vectors into the x and y components? care to refresh my memory??
  5. Oct 9, 2007 #4
    you would need to know the angle of at least one vector.

    Each force has an horizontal force component and vertical force component.

    Forces which are fully vertical have a horizontal force of 0 and vice versa.

    How to resolve them depends on which angle you are using.

    Usually it goes Fsintheta = y component, Fcostheta = x component. you have to see your graph though.
  6. Oct 9, 2007 #5
    ok ,thanks, i went back and reviewed the law of cosines
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