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Combining two equations

  1. May 19, 2007 #1
    How do I combine these two equations?

    Fc=mv(squared)/r
    Fg=qvb
     
  2. jcsd
  3. May 19, 2007 #2

    cristo

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    You need to make an effort yourself, and furthermore, defined your symbols. For example, on the LHS of each equation, you have Fc and Fg, respectively. Are these Fxc and Fxg, or are they different variables Fc and Fg?
     
  4. May 19, 2007 #3
    It is with the smaller c and g.
     
  5. May 19, 2007 #4

    cristo

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    Well, in that case, can you rearrange the second equation to get it into the form v=... ?
     
  6. May 19, 2007 #5
    Yeah, it would be v=f/qB....
     
  7. May 19, 2007 #6
    ...also I'm trying to combine the two equations to find m, which is mass.
     
  8. May 19, 2007 #7

    cristo

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    Ok, so you now have Fc=mv2/r and v=Fg/qB. Now, can you substitute the second equation into the first? [i.e. replace v^2 in the first with Fg/qb]

    Right, well if you manage to do the substitution above, then you need to rearrange the equation you obtain to get it in the form m=...
     
  9. May 19, 2007 #8
    Okay, so I substituted the second equation into the first and I got Fc=m*fg/qB/R. Is that right?
     
  10. May 19, 2007 #9

    cristo

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    No, v is squared in the first equation, and thus substituting the second into the first should yield [tex] F_c=\frac{m}{r}\left(\frac{F_g}{qB}\right)^2[/tex]. Can you rearrange this?
     
  11. May 19, 2007 #10
    m=Fcr*qB/Fg^2 :uhh:
     
  12. May 19, 2007 #11

    cristo

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    Well, you're missing a square on q and B; adding parentheses like this m=Fcr*(qB/Fg)^2 gives the correct solution.
     
  13. May 19, 2007 #12
    Oh okay. I see. Thank you very much!
     
  14. May 19, 2007 #13

    cristo

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    You're welcome.
     
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