Orbital Frequency of Electron-Positron Pair: Calculating 1.0nm Separation

[soccerref14]

Can someone tell me how or an idea on how to start this problem?

A positron is an elementary particle identical to an electron except that its charge is +e. An electron and a positron can rotate about their center of mass as if they were a dumbbell connected by a massless rod. What is the orbital frequency for an electron and a positron 1.0nm apart?

 

[praharmitra]

Find out the center of mass of the entire system. You can then assume that two particles are orbiting around their mutual center of mass. The velocity can be calculated from their mutual attractive force.