Question
(a) A cosmic ray proton moving toward the Earth at $5.00 \times 10^7 \textrm{ m/s}$ experiences a magnetic force of $1.70 \times 10^{-16} \textrm{ N}$ . What is the strength of the magnetic field if there is a $45^\circ$ angle between it and the proton’s velocity? (b) Is the value obtained in part (a) consistent with the known strength of the Earth’s magnetic field on its surface? Discuss.
1. $3.01 \times 10^{-5} \textrm{ T}$
2. This is 60% of the magnetic field strength of the Earth, and, since the Earth's magnetic field varies with position around the planet, yes, this answer is consistent with the Earth's magnetic field.
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