Q: Use dimensional analysis to find the period of a pendulum. What does it depend on? Assume T depends on length l, mass m, gravity g. [T] = T, [l] = L, [m] = M, [g] = LT⁻². T ∝ l^a m^b g^c: T¹ = L^a M^b (LT⁻²)^c. M: b = 0. T: 1 = -2c: c = -1/2. L: 0 = a+c: a = 1/2. T ∝ √(l/g) (mass irrelevant!)! True: T = 2π√(l/g) ✓!