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Determine the Charge on a Particle

  1. Sep 1, 2012 #1
    1. The problem statement, all variables and given/known data

    a.) Two equally charged particles, held 22.4 cm apart, are released from rest. The initial acceleration of the first particle is observed to be 4.0 m/s2 and that of the second particle is 6.0 m/s2. If the mass of the first particle is 3.40 x 10-7 kg, determine the mass of the second particle in kg.

    b.)For the previous problem, determine the charge on the particles?

    2. Relevant equations
    F = ma, m = f/a, e = 1.609 x 10^-19


    3. The attempt at a solution
    I am able to determine the mass of the second particle which is 2.26 x 10^-7. The second question states that we should find the charge on the particles. I tried to multiply the mass of the second particle by 1.609 x 10^-19. But i dont think that is the right formular because the unit does not cancel. Pls, is there any formula for charge?
     
  2. jcsd
  3. Sep 1, 2012 #2

    rock.freak667

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    From part a you have the force F. So for part b, you will have to apply Coulomb's Law.
     
  4. Sep 1, 2012 #3
    The SI unit of the answer is in Couloumbs (C) mean while the SI unit of coulombs law formular is N.kg^2/C^2.
     
  5. Sep 1, 2012 #4

    rock.freak667

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    Coulomb's law describes the force between two electrostatic particles. You have the force from the first part, you just need to rearrange to get the correct quantity.
     
  6. Sep 2, 2012 #5
    Hi,
    I dont really understand what you mean by rearrange to ge the correct quantity..
     
  7. Sep 2, 2012 #6

    rock.freak667

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    If your formula is something like

    F=kM/r

    you can rearrange to get M such that

    M=Fr/k


    What is the formula for Coulomb's law?
     
  8. Sep 2, 2012 #7
    F= kq1q2/r2 (Coulombs law formular)
     
  9. Sep 2, 2012 #8

    rock.freak667

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    Since the charges are equal, what does that mean for q1 and q2?
     
  10. Sep 2, 2012 #9
    It means that q1 and q2 have thesame charge and therefore they will repel each other. As we know, like charges repel and unlike charges attract.
     
  11. Sep 2, 2012 #10

    rock.freak667

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    Right so q1=q2, which means you can replace this by q2. So in F=kq2/r just rearrange to solve for q.
     
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