Physics

Problem

Uniform fields

\vec E = (3\,\hat i - 4\,\hat j)\times10^{3}\,\text{V m}^{-1}

and

\vec B = 0.40\,\text{T}\,\hat k

fill a region of space. A singly charged ion (charge

+e

) enters the region with some velocity

\vec v

. Which one of the following velocity vectors, given in units of

10^{4}\,\text{m s}^{-1}

, will allow the ion to pass straight through without any deflection? a)

(1.0\,\hat i + 0.75\,\hat j)\times10^{4}\,\text{m s}^{-1}

(-1.0\,\hat i + 0.75\,\hat j)\times10^{4}\,\text{m s}^{-1}

(-1.0\,\hat i - 0.75\,\hat j)\times10^{4}\,\text{m s}^{-1}

(-0.75\,\hat i + 1.0\,\hat j)\times10^{4}\,\text{m s}^{-1}