1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Speed of a Particle

  1. Feb 12, 2009 #1
    1. The problem statement, all variables and given/known data

    Consider the following position function.
    r(t)= et(cos(t)i+sin(t)j+7tk)

    Find the speed of a particle with the given position function.

    2. Relevant equations

    I know I take the derivative of the function but I cant seem to get speed.
    I got v=e^t(cos(t)i+sin(t)j+7(t)k)+ e^t(-sin(t)i+cos(t)j+7k)

    3. The attempt at a solution

    I just cant find the speed, i think i may be just slightly off. I currently have speed is 7e^t(t+1) which is wrong.
  2. jcsd
  3. Feb 12, 2009 #2

    You are simply using "k" part, where is your i and j part. They don't cancel out.
    Last edited: Feb 12, 2009
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook