circular path in magnetic field

[dadasolee]

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Both helium and deuterium nucleus are accelerated to the same velocity before entering a uniform magnetic field. Upon entering the region of the B field, both particles are traveling at right angles to the field, and thus end up traveling in circular paths. What is the ratio of the radii of the path of the helium nuclei to the deuterium nuclei?

Why would the mass not matter, if r= mv^2/qE? And what exactly is the mass here? proton mass? atomic mass?

The answer is 1/1... hm...

 

[RogueUnicorn]

helium has twice the charge but twice the mass, so these two things cancel and thus have the same centripetal force as deuterium

 

[jaxasp]

nvm

 

[Hemichordate]

But isotopes wouldn't have the same radii, right? (Since they have the same charges but different masses)

 

[RogueUnicorn]

yes. if you're comparing hydrogen nucleii to deuterium, it would be different, with the hydrogen having a tighter radius due having less mass.