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Homework Help: Electric Charge net force

  1. Oct 3, 2005 #1
    I'm having problems figuring this one out. Some guidance would be great! Thanks!

    Particles of charge Q1 = +75 µC, Q2 = +44 µC, and Q3 = -80 µC are placed in a line (Fig. 21-46). The center one is 0.35 m from each of the others. Calculate the net force on each charge due to the other two. (Assume the positive direction is to the right.)

    Net force on Q1

    F1=242 N
    F2=110 N

    Net force = -242N + 110N = -132 N

    Net force on Q2

    F1= 242 N
    F2= 259 N

    Net force = -242N + 259N = 17 N
    (wrong, but why??)

    Net force on Q3

    F1= 110N
    F2= 259N

    Net force = 259N + 110N = 369 N
    (wrong, but why??)

    Attached Files:

  2. jcsd
  3. Oct 3, 2005 #2
    On your force on Q2, it should be +242N, not -242N, since Q1 is pushing Q2 to the right - i.e. in the positive direction. I also calculate F2 as 258 N, not 259 N.

    On your force on Q3, it should be -110 N, since Q1 is pulling Q3 to the left - i.e. in the negative direction. Again, I got 258 N, not 259 N for F2.
  4. Oct 3, 2005 #3
    thanks for your help!
  5. Oct 3, 2005 #4
    Nooooooooooooooooooooot a problem!
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