1. The problem statement, all variables and given/known data In a certain region, a charge distribution exists that is spherically symmetric but non-uniform. When a positive point charge q is located at (r,θ,φ) near this charge distribution, there is a resulting electric potential energy for the system given by: U(r,θ,φ) = ρ(naught)a^2q/18ε(naught)(1-3((r/a)^2) + 2((r/a)^3) for r ≤ a and 0 for r ≥ a where ρo is a constant having units of C/m^3 (volume charge density) and a is a constant having units of m. Note that there is no θ or φ dependence here since the charge distribution is spherically symmetric. Determine the electric force F exerted on charge q as a function of its location (r,θ,φ) for: a) r ≤ a b) r > a Check that the units of your answer make sense. (Show your work.) 2. Relevant equations F=-∇U ∇U=dU/dr r 3. The attempt at a solution' I derived ∇U=dU/dr r from the spherical coordinate gradients and since there is no dependance on phi and theta we will just be using the r vector. therefore: d/drρ(naught)a^2q/18ε(naught)(1-3((r/a)^2) + 2((r/a)^3) r = 6r(r-a)/a^3 r This is where I don't know what to do, how would I express my answer?