Question
(a) Find the charge on a baseball, thrown at 35.0 m/s perpendicular to the Earth’s $5.00 \times 10^{-5} \textrm{ T}$ field, that experiences a 1.00-N magnetic force. (b) What is unreasonable about this result? (c) Which assumption or premise is responsible?
1. $571 \textrm{ C}$
2. Such a large charge would repel itself off of such a small object. Typical static shocks involve $\approx 5 \textrm{ }\mu\textrm{C}$
3. The $1.00 \textrm{ N}$ force is very overstated.
Solution Video

OpenStax College Physics Solution, Chapter 22, Problem 85 (Problems & Exercises) (0:52)

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This is College Physics Answers with Shaun Dychko. The force on this baseball is found using <i>F</i> equals the charge times the baseball speed times the magnetic field strength, and we can solve for <i>q</i> by dividing both sides by <i>VB</i>. So <i>q</i> is <i>F</i> over <i>VB</i>. So that’s one Newton divided by 35 meters per second times five times ten to the minus five Tesla, which gives 571 coulombs. Now such a large charge would repel itself off of such a small object, and it’s a very big number. Typical static shocks involve about five microcoulombs which is a piece of information I found from Wikipedia. So the one Newton force is very overstated and the baseball will likely experience a force much much less than that.