Consider a spatially flat, matter-dominated Universe (Ωm = Ω = 1), which is contracting with time. How does the density perturbation, δ ≡ (rho − rho¯)/rho¯, evolve with time in such a Universe? Here rho is the (average) density?

An air-filled capacitor is formed from two long conducting cylindrical shells that are coaxial and have radii of 26 mm and 103 mm. the electric potential of the inner conductor with respect to the outer conductor is - 700 v (k = 1/4πε 0 = 8.99 × 109 n · m2/c2) the energy stored in a 1.0-m length of this capacitor is closest to