Actual Physics requires a lot of derivation of equations to produce a result, a firm understanding of computing equations would be a prerequisite before you could try deriving an equation.
One thing to consider is that if you decide to go into Physics, you will most likely have to get a PHD if you want to work in the Physics field. Thatís 4 years for a B.Sc, another 4 for a PHD and after that you would have to do 1-2 post docs where you work at a university. This is a fairly long road ahead of you, and you should be aware of that.
In my case, I was a Physics student, but after two years of study, I realized that although I really liked Physical Concepts, I wasn't so found of actual Laboratory work, which as a Physicist you would be doing a lot of. So even though I finished my last semester with an A- average, I've switched programs.
So my advice to you is before you make any switch, you have to take a couple of Physics/Mathematics courses, and you should also take a semester long Physics Laboratory course for good measure. If after all that, you find that you're enjoying the course material than you should switch into a Physics program, if not then you're better off staying in Law.