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Homework Help: Proton being accelerated

  1. Mar 5, 2009 #1
    1. The problem statement, all variables and given/known data

    A proton (mass m = 1.67x10^-27 kg) is being accelerated along a straight line at 2.0x10^15 m/s^2 in a machine. The proton has an initial speed of 2.4x10^7 m/s and travels 2.5 cm.

    (a) What is its speed?

    (b) What is the increase in its kinetic energy?

    3. The attempt at a solution

    Is it ok to have no idea where to begin?

    I know F=ma, and that V=Vo+1/2at... but I can't see how that helps.

    Help me begin?
    Last edited: Mar 5, 2009
  2. jcsd
  3. Mar 5, 2009 #2


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    You just need two equations.

    Kinetic energy.

    And an equation that relates Velocity, distance and acceleration.
  4. Mar 5, 2009 #3
    no lowly pion you are wrong what he needs is the other SUVAT equations namely.

    S=0.5(u+v)t then rearrange to get V
    (u is intitial velocity)

    then you put that into the the kenetic energy equation


    then you have got your anser
  5. Mar 5, 2009 #4


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    And what is the time the proton is in the machine?
  6. Mar 5, 2009 #5

    So, using v^2 = v_0^2 + 2a(Delta x), I can find the final velocity I think. For the delta x part, would it be (2.5 - 0)?

    And can I use KE= 1/2mv^2 to find the kinetic energy? If so, wouldn't I use the final velocity found in part a for "v"?

  7. Mar 5, 2009 #6


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    Yes the V2 = Vi2 + 2ax should do you well.

    Part b) is looking for ΔKE. So you are needing to calculate the final KE and subtract the initial.
  8. Mar 5, 2009 #7
    Ahhhh so I do change in KE=m(v_f)^2 - m(v_i)^2 , right?
  9. Mar 5, 2009 #8


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    Half right anyway.

    ... i.e don't forget the 1/2.
  10. Mar 5, 2009 #9
    haha yes! I knew that I was just typing in a hurry.

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