I wouldn't call myself a physics educator, but I have TAed many physics courses, and I had a temporary employment at my university's physics department working on constructing new numerical term projects for undergraduate introductory physics. And really, electric forces and gravity are both 1/r^2 laws, and the field near the surface of a biological membrane is also fairly uniform, so why not calculate the forces on a virus instead? It's a matter of piqueing the interest of the students.

I remember constructing one numerical assignment for intro phys. for mech. eng. that was supposed to teach numerical integration of ODEs, so I had them set up Newton's second law for a soccer penalty kick, working their way up to including realistic air resistance plus Magnus effect. Boy, they were excited to be able to curve that ball past the keeper into the upper corner of the goal (this was Matlab and I gave them code to draw the path in 3D on a soccer field).