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!

Instantaneous velocity from avg velocity with constant accelartion

  1. Feb 17, 2012 #1
    1. The problem statement, all variables and given/known data
    With constant acceleration prove that the average velocity from t1 to t2 =t1 + Δt is equal to the instanous velocity in the middle of the time interval between t1 and t2.


    2. Relevant equations
    What I am looking for is a general equation that does not involve accelaration. All I have is position. By the way this is 1-D kinematics so no need for vectors.



    3. The attempt at a solution
    Tried all sorts of subs with Vavg= (Vi + Vf)/2 and Vavg= Δx/Δt I tried subbing these in to many of the other equations such as Vf=Vi+at. I imagine there is some sort of trick to it. This thing is driving me nuts.
     
    Last edited by a moderator: Feb 18, 2012
  2. jcsd
  3. Feb 17, 2012 #2
    Re: Instananous velocity from avg velocity with constant accelartion

    It can be shown this way I believe. Here's a hint:
    Vavg= (Vi + Vf)/2
    Vavg= (Vi + Vf)/2 - Vi +Vi
    Vavg= (Vf - Vi)/2 +Vi
     
  4. Feb 18, 2012 #3
    Re: Instananous velocity from avg velocity with constant accelartion

    Alright still having a hard time. I got it into that form that you mentioned and was able to get Vavg=2Vf-(3at)/2 which there is a t/2 in there. Good sign I suppose but it just doesn't seem right since I am going to have to use a distance traveled to find it. I will play around with it some more but feel I'm coming to dead ends.
     
  5. Feb 18, 2012 #4

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Re: Instananous velocity from avg velocity with constant accelartion

    Can you express in math what it is exactly that you're trying to show? In other word, what equation says "the average velocity from t1 to t2 is equal to the instantaneous velocity in the middle of the time interval between t1 and t2"?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Instantaneous velocity from avg velocity with constant accelartion
  1. Avg Velocity (Replies: 12)

Loading...