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Angle between magnetic field B and velocity of charge

  1. Mar 3, 2014 #1
    1. The problem statement, all variables and given/known data

    Find magnitude and direction of F of a charge moving through a magnetic field.

    velocity: 5 m/s
    charge: 2 C
    B: 3 T (pointing out of the page when drawn)

    2. Relevant equations

    (vector)F=qv x B
    (magnitude)F=qvBsinθ


    3. The attempt at a solution

    I know to use the equation for magnitude but I'm confused as to what the angle would be between v and B. Since the magnetic field is pointing out of the page, would the angle be 90°, making sin(90)=1?

    Also, don't know what direction that would be. Since I don't know the direction of B, I'm not sure how to use the right hand rule to figure this out.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 3, 2014 #2

    rude man

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    You do know the direction of B. It's out of the page.

    Unfortunately, the problem does not define the direction of v so you can't solve it.
     
  4. Mar 3, 2014 #3
    Sorry, forgot to mention that: the velocity moves straight from left to right.
     
  5. Mar 3, 2014 #4

    rude man

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    OK, so place a sheet of paper on the table, draw an arrow from left to right = v, then hold a pencil at the back end of the arrow pointing straight up (B).
    What is the angle between the arrow and the pencil?
     
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