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Can someone clarify some things for me?

  1. Sep 16, 2011 #1
    I don't know if I am just looking too much into the problems or what, but I am having a very hard time determining what is what in the problems. I am not confident on what I pick as Vnaught, V, x, y, etc .... Will someone please help?
    I will tell you how I determine it, and you can correct me.

    x=where it lies on the x axis?
    y=where it lies on the y axis? ... Both of these are determined by me? Correct?

    So is V the velocity of the object? And what is Vnaught?

    These are all pertaining to 2D equations.
  2. jcsd
  3. Sep 16, 2011 #2
    Naught is usually the initial value of something. If you have a position graph then you could say that x naught is the starting position of the object. You see subscripts used a great deal. i usually denotes an initial value as well, f usually means the final value. Aside from that everything else is pretty descriptive. When you are dealing with 2+d problems, you might see subscripts of x and y to let you know which component it is. Say you have a vector r, they might say that [itex]a_{rx}[/itex] is the acceleration of the x component of the r vector and so on.
    Last edited: Sep 16, 2011
  4. Sep 16, 2011 #3


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    Staff Emeritus
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    Gold Member

    Yes, x and y are positions, measured along their respective coordinate axes.

    v is velocity. In general it varies with time (i.e., pick a time t, and you'll get a specific value for v).

    v0 is initial velocity (i.e. velocity at t = 0).
  5. Sep 16, 2011 #4
    So what is V?
  6. Sep 16, 2011 #5


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    In the context you have provided, V would be the velocity at the time to are dealing with.

    Vo is the initial velocity. V is the velocity later.

    eg: you might want to know "if a stone is thrown vertically down from the top of a 30m tower with a velocity of 2 ms-1, how fast will it be travelling just before it hits the ground -[take g=10].

    everything is happening downwards, so let down be positive.

    Vo = 2.0
    a = 10
    x = 30
    V = ??

    Best formula to use would be

    V2 = Vo2 + 2as

    V2 = 4 + 2x10x30 = 604

    so V = 24.6
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