What is the mass of the ion

  • Thread starter shimizua
  • Start date
  • #1
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Homework Statement


A mass spectrometer applies a voltage of 2.00 kilovolts to accelerate a singly charged ion (+e). This ion then enters a region of uniform magnetic field (B= 0.400 T) which then bends the ion into a circular path of radius 0.305 m What is the mass of the ion?


Homework Equations


after breaking everything down from F=ma i got to m = (qB^2r^2)/2V


The Attempt at a Solution


well i am just unsure of how to find q. I know that V=2kV, B=.4 T, and r=.305 m. so if you can just help me with finding q. i can do that rest
 

Answers and Replies

  • #3
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ok well so i tried doing the m= -1.602x10^-19(.4^2)(.305^2)/4 and got -5.96x10^-22. would it be in kg though?
 
  • #4
LowlyPion
Homework Helper
3,097
5
ok well so i tried doing the m= -1.602x10^-19(.4^2)(.305^2)/4 and got -5.96x10^-22. would it be in kg though?

To put it in perspective for a single proton:
Wikipedia said:
1.672621637(83)×10−27 kg
 
  • #5
The conundrum you got going here is that the charge is +e, not e. SOO...in taking your big step in finally realizing that q is given as the charge +e, you can now go figure that the charge is POSITIVE (1.6*10^-19 C), not negative.
 

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