We went over problems involving electric forces.
For one the horizontal components of the forces canceled out, using that information, we could calculate the sum of the vertical forces and figure out the charges by using Coulomb’s Law.
You can either use trig functions or the Pythagorean Theorem, or a combination, for some of these problems.
Labeling things with subscripts becomes more important once the problems get more complicated.
One problem involved early kinematic equations.
To figure out the units for something, like electric field, you can use the simplest equation you know for that thing and go from there.