Chapter 20, Problem 22P

An electron of mass $\text{9}\text{.1}\times {\text{10}}^{\text{31}}$ kg moves horizontally toward the north at $\text{3}\text{.0 }\times {\text{10}}^{\text{7}}\text{m/s}$. Determine the magnitude and direction of a $\stackrel{\to }{B}$ field that will exert a magnetic force that balances the gravitational force that Earth exerts on the electron.