Physics

Problem

A pollen grain of mass

4.2\times10^{-7}\,\text{kg}

carries a charge of

+8.0\times10^{-10}\,\text{C}

. What magnitude and direction of uniform electric field will keep the grain motionless in Earth’s gravitational field? Use

g = 9.8\,\text{m}\,\text{s}^{-2}