> Dimensional Analysis - Buckingham pi?

Dimensional Analysis - Buckingham pi?

Posted at: 2014-06-09 
Given: Energy is a function of shockwave radius R, density of atmosphere p, and time since explosion t. Use dimensional analysis to show that R is equal to some constant times a function of E, p, t. To do this would I just find the dimensionless parameters (pi_1, pi_2, etc) then show that pi_1 (which would contain R) is a function of (pi_2, pi_3, etc)? Where does the constant come in? Also, why would it not be correct to say that R = C*f(E,p,t) + C2, where C and C2 are constants?