Yup. I expect P1 and P2 are correlated(moderately to strongly).
Using the equation below, we can come up with the idea of correlation.
Var(aX+bY) = a^2 Var(X)+ b^2 Var(Y) + 2ab*Cov(X,Y)
How do you define physical significance?.
May be the following link may helpful for the rest of the questions