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Homework Help: Velocity and position of electron

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data

    An electron's position is given by R= 3t i + 4t^2 j + 2k, where t is in seconds and R is in meters. What are the (a) x-, (b) y- and (c) z-components of the electron's velocity? (d) What is the electron's speed? (e) What angle does the electron's velocity make with positive x-axis? Give all answers as appropriate functions of time.

    2. Relevant equations

    3. The attempt at a solution
    So far, I have the
    x-component = 3
    y-component= 8t
    z-component= 0

    I have no idea how to find the speed, of the angle it makes. For the speed I put 3 + 8t, and it was wrong. I have one more try at the problem.
  2. jcsd
  3. Sep 15, 2009 #2
    Re: Velocity

    Speed is just the magnitude of the velocity (I.e. velocity without the direction part).

    You have the components of the velocity vector how would you normally find the angle?
  4. Sep 15, 2009 #3
    Re: Velocity

    Ok so are you saying the speed is equal to 3^2 + 8^2...then take the square root of that??

    And the angle is inverse tan of 8/3???
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