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Cant understand the velocity?

  1. Nov 1, 2007 #1
    ok just say you have these values:

    s=1.3m
    u=0ms
    v=?
    a=10
    t=0.5099

    Now these values represent the vertical part of a vector..

    now to work out velocity it uses a formula, v=s/t, = 1.3/0.5099 = 2.55ms... which is incorrect.. .

    but using this formula.. v^2=u^2 + 2as
    Plug in all the values
    v= 5.1ms

    why does this occur? is the velocity formula (s/t) only used when an object is in linear motion??
     
  2. jcsd
  3. Nov 1, 2007 #2

    learningphysics

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    Homework Helper

    v = s/t is only for constant velocity motion... ie when acceleration = 0.

    for accelerated motion, you can say average velocity is s/t... but your question is asking for v which is final velocity...

    you will notice that:

    average velocity = (u + v)/2

    s/t = (u+v)/2

    2.55m/s = (0 + v)/2

    gives v = 5.1m/s.

    so you can think of it like that. But I recommend to only think of v = s/t for constant velocity motion...
     
  4. Nov 1, 2007 #3
    thankyou again!
     
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