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# charged particle in circular orbits watch

1. guys anything comes in mind about this?im absolutely lost with this.
in a mass spectrometer a beam of ion at a speed of 7.6x10^4 was directed into a uniform magnetic field of flux density 680mTa)An ion was deflected in a semi-circular path of diameter 28mm on to the detector . calculate the specific charge of the ion.
Justifications : if we want to calculate specific charge, we have to use Q/m which has two unknowns and i tried to write m in terms of Q when you rearrange equation r=mv/bg to find m which is(m=rBQ/V) but I'm not sure if I'm on the right path .any help would be much appreciated .
2. Specific charge is Q/m, you don't have two unknowns, only one. All you need to know is the ratio Q/m (not Q and m).

This suggests there is some way to find Q/m without knowing Q or m separately.

Try writing down the equation for circular motion (in terms of acceleration), then write down Netwon's 2nd law, then write down an expression for the force acting on a moving charge in a magnetic field. Don't use numerical values, stick to the algebra. Then see if you can re-arrange the equation to make "Q/m" the subject.

After that, you can substitute in numbers.
3. Thanks mate

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