1. Not finding help here? Sign up for a free 30min 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!

Deriving a kinematic equation.

  1. Sep 11, 2007 #1
    1. The problem statement, all variables and given/known data

    Derive (v_f)^2 = (v_i)^2 +2ad

    2. Relevant equations

    (v_f)^2 = (v_i)^2 + 2ad
    (v_f) = (v_i) + at
    d = (v_i)t + \frac{1}{2}at^2

    3. The attempt at a solution

    I have attempted to replace the variables with others from other kinematic equations such as v_f = v_i + at. However, I am getting no where. I have also taken the derivative of the equation (or so I think) but if I have not done it correctly, then I am just going no where.

    When taking the derivative of the equation (v_f^2 = v_i^2 + 2ad) I remembered dv/dt = a , a in this equation is constant, and dd/dt = v, thus I got 2a=2a+2v and once simplified brings me to 0=v? I feel I am deriving the equation incorrectly.

    Now, after having exhausted my thoughts, I've come asking for help.
  2. jcsd
  3. Sep 11, 2007 #2


    User Avatar
    Homework Helper

    Are you supposed to derive the equation from first principles? What i mean is are you allowed to use:

    [tex]d = (v_i)t + \frac{1}{2}at^2[/tex]
  4. Sep 11, 2007 #3
    Yes. I can use any type of equation. And any principles. I'm just at a loss as to how to get started. I should be fine with a little nudge in the right direction.
  5. Sep 11, 2007 #4


    User Avatar
    Homework Helper

    You can solve for t, in the equation vf = v0 + at... then substitute t into the d equation posted, that will give you the result.
  6. Sep 11, 2007 #5
    Thank you. I've got it now. I had returned to using the other equations, but the word "derive" kept making my brain do derivatives. I guess that's what I get for being a math minor and taking as few physics classes as possible.

    Thank you, again.
  7. Sep 11, 2007 #6


    User Avatar
    Homework Helper

    no prob.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Deriving a kinematic equation.
  1. Kinematic Equations (Replies: 8)

  2. Kinematic Equations (Replies: 2)

  3. Kinematic Equations (Replies: 36)