1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Question on force

  1. Nov 16, 2011 #1
    if two forces act simulataneously on a body how can we show than one force does not effect the action of the other force? (provided they are acting obliquely)
    Specifically, how can we show that the acceleration of one force remains the same in that direction?
     
  2. jcsd
  3. Nov 17, 2011 #2

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I'm not sure what you're asking. Forces obey the superposition principle. The basic idea is that the total force acting on a body is the vector sum of all the individual forces acting on that body.
     
  4. Nov 17, 2011 #3
    sorry u didnt understand my question. i ask it again: how is the parallelogram addition proved?
     
  5. Nov 17, 2011 #4

    Matterwave

    User Avatar
    Science Advisor
    Gold Member

    You posit that forces are vectors. Vectors obey the parallelogram law.

    This is true by definition. What's the prove?
     
  6. Nov 17, 2011 #5
    did i?
    somebody help me with this
     
  7. Nov 17, 2011 #6
    actually the first question is what i want. parallelogram follows from it.
    if two forces act simulataneously on a body how can we show than one force does not effect the action of the other force? (provided they are acting obliquely)
     
  8. Nov 17, 2011 #7

    Matterwave

    User Avatar
    Science Advisor
    Gold Member

    You essentially want a proof of a definition. This was what I was trying to get at. Force is defined to be a vector quantity, therefore forces add by vector addition.
     
  9. Nov 17, 2011 #8
    why is force a vector? why not electrical current?
     
  10. Nov 17, 2011 #9

    Matterwave

    User Avatar
    Science Advisor
    Gold Member

    It's a definition. What much else can I say? You make models of how the universe works. In those models you need to make some clear definitions. If your model describes the universe correctly then you keep it, if not, you get a new model.

    I don't get what you are looking for.
     
  11. Nov 17, 2011 #10
    my question arised when the vector addition of acceleration was not clear in my mind
     
  12. Nov 19, 2011 #11
    Newton described the concept that forces act independently and add as a parallelogram as:

    “A body, acted on by two forces simultaneously, will describe the diagonal of a parallelogram in the same time as it would describe the sides by those forces separately.”

    This was done before the concept of vectors and is one of the reasons that vectors are defined the way that they are. Presumably Newton and others got the notion from observation and experiment. I don't know what setup they used to prove it but if you want to show that two forces acting simultaneously on a body don't affect each other you'll have to go to the lab measure the affect of one force then the other applied individually and then measure them applied simultaneously.

    I feel like there should be a standard classroom experiment to show this but I can't think of one off hand.
     
  13. Nov 19, 2011 #12
    I have a question too
    what should be the value of the work,if vertical component is 2/3 time to the hoizontal component of the applied force,while the displacement in the direction of applied force is x metres?
    plz give me a complete solution.....
     
  14. Nov 19, 2011 #13

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, we don't do your homework for you here. Please read the forum rules. If you have given the problem a decent attempt and need help/guidance, then post your question in the homework help section *using the template* provided for homework help posts (in which you must show your attempt so far).

    Also, please post separate topics in separate threads -- don't hijack other people's threads
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Question on force
  1. Force question (Replies: 2)

  2. Force Question (Replies: 3)

  3. A question on Forces (Replies: 6)

Loading...