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!

Average velocity problem

  1. Sep 5, 2012 #1
    1. The problem statement, all variables and given/known data

    A falling object moves so that its height x above the ground at time t is given by the following equation: x = 100 m - (4.9 s-2)t2. Find its average velocity from t = 0 t t = 2 s.


    2. Relevant equations

    Average velocity = Δx/Δt

    3. The attempt at a solution

    I was able to work it out to the point where I solved for x by plugging in the times given for 0 secs and 2 secs.

    For t = 0:

    x = 100 m - (4.9 s -2 * (0 s)2

    = 100 m

    For t = 2:

    x = 100 m - (4.9 s -2 * (2 s)2

    = 19.6 m

    Solving for t2 in the equation, I get:

    100 m/4.9 s-2 = t2

    Final answer of 4.52 m s -2

    For the average velocity equation (and t), I realize this does not work all that great as m will be cancelled in setting up the average velocity equation and am only left with seconds for time. I'm not sure what it is that I'm doing wrong in this problem. Thank you everyone for your help.
     
  2. jcsd
  3. Sep 5, 2012 #2

    PeterO

    User Avatar
    Homework Helper

    Average velocity is just (final position - initial position) divided by time interval.
    You have successfully found the initial and final positions.
    You just need the time interval.

    How long was it from t = 0 to t = 2 ?
     
  4. Sep 5, 2012 #3
    Oh ok, got it! I guess I was just overthinking it, oops :redface:...Thanks a lot! :biggrin:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook