1. The problem statement, all variables and given/known data For part d), how to show that they are inversely proportional to each other ? The mark scheme states: "Correct calculation to check inverse proportionality. √h x cosϑ = k. Sensible comments relating to calculations to within 20% or their own value and suggested relation." What do they mean by 20%? 2. Relevant equations Percentage uncertainty = (uncertainty/measured value) x100% 3. The attempt at a solution My values are, √h = (2.95±0.1) cm, cos θ = 0.50. k1 = 2.95 x 0.50 = 1.475 √h = (2.30±0.1) cm, cos θ = 0.64, k2 = 2.30 x 0.64 = 1.472 I calculated the percentage difference of k, ((1.475-1.472) /1.472 ) x 100% = 0.2% Then I calculated the uncertainty of √h = (0.1 / 2.30) x 100% = 4.3% This is the method I followed from a textbook, so what does the 20% in the mark scheme represents ? Hope you all understand what I'm doing here..