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!

Homework Help: Cant understand the velocity?

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


    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


    User Avatar
    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!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook