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: Instantaneous velocity problem

  1. Sep 11, 2008 #1
    1. The problem statement, all variables and given/known data
    find the instantaneous velocity of the particle described in figure 1.1 at the following time a.) t=3.0 s.

    2. Relevant equations
    instantaneous velocity equals dx/dt
    in the graph, 3 seconds of time is equal to 8 meters.

    3. The attempt at a solution

    so would the answer just be the derivitive of 8/3? i dont get how to use the formula. because then the answer would just be zero, right?
  2. jcsd
  3. Sep 11, 2008 #2
    dx/dt gives you the slope of the tangent drawn to point at which you need the instantaneous speed. I presume that you have a displacement versus time graph. Draw a tangent to the point at t=3 and fine the slope of the tangent.
    Otherwise more accurately, if you could express displacement as a function of time from the structure of the graph an then differentiate it, it would be better.
  4. Sep 11, 2008 #3
    if the acceleration is zero (a=0) then x=v*t+x0 so the answer is 8=v*3+x0 and if x0=0 then the answer is v=8/3
    and also v=dx/dt then dx=v*dt and if you integrate this equation you will get x-x0=v*t
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook