Magnetism and Centripetal force question

AI Thread Summary
To determine the mass of a singly charged ion making 7 revolutions in 1.3 x 10^-3 seconds within a 4.5 x 10^-2 T magnetic field, the relevant equation is m = qBT/2π. The orbital period T must be calculated as (1.3 x 10^-3 seconds) / 7. Substituting the values into the equation allows for the calculation of the mass. The discussion confirms that this approach is correct for solving the problem.
jumpfreak
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Homework Statement



One method for determing masses of heavy ions involves timing their orbital period in a known magnetic field. What is the mass of a singly charged ion that makes 7.0 revolutions in 1.3 x 10^-3 seconds in a 4.5 x 10^-2 T field.

a) 2.1x10^-25 kg
b) 1.3x10^-24 kg
c) 6.5x10^-23 kg
a) 5.0x10^-20 kg

Homework Equations



I'm not sure of which equation to use. Maybe...
Fc = Fb
m4(pi^2)r/T^2 = QvB



The Attempt at a Solution



m4(pi^2)r/(1.3x10^-3s/7)^2 = Qv(4.5x10^-2)

This might be the wrong formula.
 
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jumpfreak said:

Homework Statement



One method for determing masses of heavy ions involves timing their orbital period in a known magnetic field. What is the mass of a singly charged ion that makes 7.0 revolutions in 1.3 x 10^-3 seconds in a 4.5 x 10^-2 T field.

a) 2.1x10^-25 kg
b) 1.3x10^-24 kg
c) 6.5x10^-23 kg
a) 5.0x10^-20 kg

Homework Equations



I'm not sure of which equation to use. Maybe...
Fc = Fb
m4(pi^2)r/T^2 = QvB



The Attempt at a Solution



m4(pi^2)r/(1.3x10^-3s/7)^2 = Qv(4.5x10^-2)

This might be the wrong formula.
It is the right formula.

If mv^2/r = qvB where v = 2\pi r/T then:

qB = m2\pi/T

m = qBT/2\pi

Just plug in the numbers.

AM
 
One caution:

In the previously cited equation m = qBT/2\pi, T is the orbital period = (1.3 x 10^-3)/7 sec
 
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