Answer:
ρ = 1.8 kg / .90 m = 2 kg / m linear density
Γ = m g L/2 = I α torque producing acceleration α
α = m g L/2 / I = m g L/2 / 1/3 m L^2 = 3 g / (2 *L)
α = 3 / 2 * 9.80 * / .90 s^2 = 16.3 / s^2 angular acceleration
a = L/2 α = .90 m / 2 * 16.3 / s^2 = 7.3 m/s^2 acceleration of middle of rod