Question

A proton travelling at $ 23{}^\circ C $ w.r.t. the direction of a magnetic field of strength 2.6 mT experiences a magnetic force of $ 6.5\times {{10}^{-17}}N $ . What is the speed of the proton?

• A. $ 2\times {{10}^{5}}\text{ }m/s $
• B. $ 4\times {{10}^{5}}\text{ }m/s $
• C. $ 6\times {{10}^{5}}\text{ }m/s $
• D. $ 6\times {{10}^{-5}}\text{ }m/s $

Answer 1

Answer: (B)

$ F=qvB\sin \theta $ $ v=\frac{F}{qB\sin \theta } $ $ =\frac{6.5\times {{10}^{-17}}}{26\times {{10}^{-3}}\times 1.6\times {{10}^{-19}}\times 0.39} $ $ v=4\times {{10}^{5}}m/s $