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Homework Help: Basic Acceleration and Distance Problem

  1. Oct 11, 2009 #1
    1. An electron in a crt accelerates from 14200 m/s to 3.73x10^6 m/s over 1.93 cm. how long does the electron take to travel this distance? and What is it's acceleration (in m/s^2)

    The supposedly "easiest" question on my physics worksheet has me stumped. I know that I have to convert so it would be 1420000 cm/s and 373000000 cm/s , but I'm am stuck because I do not know the time or acceleration? I just don't know what equation to use?! I appreciate anyones help.

    Thank You.
  2. jcsd
  3. Oct 11, 2009 #2


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    Homework Helper

    Hi balllla, Welcome to PF.
    From the set of kinematic equations, find out the equation, which relates initial velocity, final velocity, displacement and acceleration.
  4. Oct 11, 2009 #3
    LaTeX Code: v^2 = v_0^2 + 2 a \\Delta x

    Would I use this equation which would find out the acceleration to later find out the displacement.?
  5. Oct 11, 2009 #4
    I would convert the 1.93 cm to 0.0193 m instead.
  6. Oct 11, 2009 #5
    ok but what actually am I trying to find. Am I trying to find time and are 14200m/s and 3.73 velocity?
  7. Oct 11, 2009 #6
    would this work

    3.73x10^6 ^2= 14200m/s^2 + 2a(.0193m)

    ?????? what would that give me, my acceleration? but I still don't know how to do the first part of the problem.

    many thanks.
  8. Oct 11, 2009 #7
    I believe you meant "time" instead of "displacement".
    Put the velocities into m/s instead of cm/s and put the distance into meters.

    Okay. Tell us which of those given numbers you think are the Vi, Vf, X, a, and t. Just label and list them. Then finding an equation should be simple.

    You are trying to find the acceleration and the time.
  9. Oct 11, 2009 #8
    vi=14200 m/s
    vf=3.73x10^6 m/s
  10. Oct 11, 2009 #9


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    Homework Helper

    You are correct. It is a large number. Proceed.
  11. Oct 11, 2009 #10
    Are you sure? Would the v^2 on the left side of the equation be the final velocity or the average velocity? I'm not trying to confuse anyone, just asking.
  12. Oct 11, 2009 #11
    OK. My acceleration is approx. 360432600000000 m/s^2. When doing the algebra I get an answer of .00000001 seconds for time, but my online computer software is saying it is wrong, I know that my acceleration is right but how is my time wrong?!
  13. Oct 11, 2009 #12


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    Homework Helper

    I am getting 1.0345^-8 s.
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