F = (m x v^2) / R
a. If F increases, what in the right hand equation must R do? R divides into (m x v^2) to create F. If F goes up, and (m x v^2) stays the same, then R must do what? R must go down or decrease. Do you see that there is an "inverse" relationship between R and F if (m x v^2) remains unchanged?
b. F and m: If F decreases and goes down, and v^2 and R remain unchanged, what must m do? Well, if F decreases, m must also decrease linearly, do you see that?
c. F and v: If F goes up, and m and R remain constant, how will v^2 react? F increases, v must also increase as well. But, because v is squared, it will increase as the "square" to F.
Let's say F = 2 and v = 3: If F increase by 1 to 3, then v increase by 4^2 = 16; if F increases by 1 again, v increases 5^2 or 25. Do you kind of see the "nonlinear" relationship there?
Plug some different numbers in for F, m, v, and R, and just play with the equation a bit.