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Uncertainty propagation errors — not multiplying percentage uncertainty by powers
“Many did not recognise the need to multiply the percentage uncertainty in the volume by three. Some incorrectly multiplied the percentage uncertainty in mass by three.”— Paper 2, March 2025
How to fix: If a quantity is raised to a power: multiply the percentage uncertainty by that power. Volume = length³, so %uncertainty in V = 3 × %uncertainty in length. Speed = distance/time, so %uncertainty in speed = %uncertainty in distance + %uncertainty in time. For ½mv², %uncertainty in KE = %uncertainty in m + 2 × %uncertainty in v.