WEBVTT
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This is College Physics
Answers with Shaun Dychko.
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The force due to the magnetic
field on the charge is
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the charge times its speed times
the magnetic field strength.
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This is assuming the charge velocity is
perpendicular to the magnetic field
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which it is, in this question.
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And that magnetic force is
going to be providing
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the centripetal force of the
charge needs to go in a circle.
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And so the centripetal force
is the mass of the charge
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times its speed squared divided
by the radius of the circle.
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So we can solve this for *B* by
dividing both sides by *qv*.
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And we get that the magnetic
field is *mv* squared over *qvr*.
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And so one of the *v* is cancel and
we end up with *mv* over *qr*.
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So the magnetic field strength
is the mass of the proton
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which is 1.67 times ten to the minus
27 kilograms times the speed
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which is 7.5 times ten to the
seven meters per second
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divided by the charge on the proton
which is the elementary charge
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1.6 times ten to the minus 19 Coulombs
times the radius of the path
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which we're told is 0.8 meters, giving us
magnetic field strength of 0.979 Tesla.