Daily Physicist

Today is the birthday of

• David Gross (1941-).
• Heinz Pagels (1939-1988).

Today’s Problem

What is the force on an electron traveling at the solar wind velocity of 400 km/s and going in a direction perpendicular to the Earth’s magnetic field of 45 \(\mu\)T?

Answer

Using the magnetic component of the Lorentz force law

\[\begin{eqnarray} F&=&q_e\vec{v}\times\vec{B}=q_evB\sin(\pi/2)=q_evB\nonumber\\ &=&(1.602\times 10^{-19}\,\text{C})(400\times 10^{3}\,\text{m/s})(45\times10^{-6}\,\text{N}\cdot\text{s}/(\text{C}\cdot\text{m}))\nonumber\\ &=&2.9\times 10^{-18}\,\text{N}\nonumber \end{eqnarray}\]