Answer
$p=qBr$
Work Step by Step
See Example 20-6. The magnetic force is the centripetal force.
$$qvB=m\frac{v^2}{r}$$
Cancel out a factor of v.
$$qB=\frac{mv}{r}$$
The momentum p is mv.
$$qB=\frac{p}{r}$$
$$p=qBr$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.