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Webassign problem

  1. Mar 29, 2008 #1
    Compute the electric field at a point .033 cm from q2 along a line running toward q3 in the figure below
    square with charges -10uC on top left and top right and on the bottom +5uC on both left and right. q1 top left q2 top right q3 bottom right q4 bottom left I need the magnitude __N/C each side of the square is .1 m by the way


    2. Relevant equations
    kq/r^2


    3. The attempt at a solution

    6.71641791x10^5-q4 to test charge
    3.10580441x10^6-q3 to test charge
    8.26446281x10^7-q2 to test charge
    8.11615113x10^6-q1 to test charge

    angle facing test charge on top triangle- 18.2629 degrees
    angle facing test charge on bottom triangle- 33.8221 degrees

    my friend told me to do this form here to get the answer but i am so confused

    "ok now break down the fields into x and y components based on those angles. the x and y for the 2 triangles. Basically the 2 sides find the field on those 2 sides
    using the field u found and the angle and sin and cos. Then u take the x and y each triangle and add them up --- x+x and y+y. then add the other 2 fields u got the the the y total. Now take the x total and the new y total and pythagorize that and that is the answer.
     
  2. jcsd
  3. Mar 29, 2008 #2
    i do not know how to finish this problem if someone could help me it would be appreciated thanks
     
  4. Mar 29, 2008 #3
    if you don have an acount on this website, aim me on mynameisbuddyl if you can help me
     
  5. Mar 29, 2008 #4
    bump* need answer..
     
  6. Mar 30, 2008 #5
    hey guys its been like 24 hours thanks for the help i appreciate it!
     
  7. Mar 30, 2008 #6

    dynamicsolo

    User Avatar
    Homework Helper

    Here's a few things you should keep in mind about the Homework Forum:

    This is not a staffed site or a technical support service. The people who help with problems here are other forum members, mostly other students, mostly helping out in bursts or short stretches, and all of them unpaid.

    A problem with a complicated description is less likely to be dealt with quickly than one where one of the people helping can see quickly what to suggest. Since this one has no picture, but a lot of numbers halfway down the first post, a lot of people looking in on it will decide to defer it to later and go help someone with something that can be answered right away.

    Bumping your own thread is not a good idea here. Nothing stays at the top of the list for very long. All "bumping" does is run up the reply count and make the thread look active, when in fact it isn't getting dealt with.

    So saying all this, I'm sorry you had to wait, but I've seen lots of threads that waited for over 12 hours because the readers present at the time apparently thought it would take too long to deal with.

    I have a question about your first sentence. Is that distance supposed to be .033 cm, or .033 meters. I think it's the latter, since .033 cm (.33 mm) would be really close to q2, the field of which would dominate everything else at that distance.

    Have you discussed in your course how to work with rectangular components of forces and fields? I ask because trying to work a problem like this out using angles and trigonometry makes it painfully difficult to work on. It will be far easier to add components.

    Try setting the problem up this way. Put the origin of a coordinate system at q3, so
    q1 is at (0, 0.1 m), q2 is at (0.1, 0.1), and q4 is at (0.1, 0). What are the coordinates of the point where they want you to measure the field? It will be easier to find distances and components this way than by setting up triangles. If the "test charge" is where I think it's intended to be, there's a way to solve this problem where you only use the field calculation kq/(r^2) once (which may have been the intention).

    BTW, what are these? Are they distances squared? Your discussion doesn't explain this (which is probably another reason this was getting passed by).

    6.71641791x10^5-q4 to test charge
    3.10580441x10^6-q3 to test charge
    8.26446281x10^7-q2 to test charge
    8.11615113x10^6-q1 to test charge
     
    Last edited: Mar 30, 2008
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