All KINDS of stuff. Mostly ideas... politics, science, religion, fishing, food ....stuff that your mom told you wasnt polite to discuss.
Actualy, Newtons work (F=mA, etc) is more correctly called "Laws" which sounds like it should be some rock solid Truth, but as we just saw, it wasnt. A "Law" is just a way of accurately describing how something works. Ohms law says Voltage is directly proportional to Current and also directly proportional to Resistance (E=I*R), but doesnt beging to even try to deascribe the mechanism of the "why" behind it. Thats what theories are for.