A student's pendulum has length from the pivot to the centre of a steel ball across
PHYSICS · Multi-part · Fermi University Physics · Scientific Practice & Experimental Methods · Uncertainty in measurement · Records, communication and the epistemology of evidence
Measurement and Method, Ch Models, idealisation and what a measurement is evidence for
Problem
A student's pendulum has length L=0.500m from the pivot to the centre of a steel ball 40.0mm across, and the combined standard uncertainty of the g it gives is 0.24 per cent of g. A ball of radius r makes the point-bob formula return g low by the fraction 0.4(r/L)2.
((a)) Find the fractional effect of the point-bob idealisation on g, in per cent.
((b)) Find the shift Δz it would cause if left uncorrected.
((c)) Decide, using the working line of about a fifth, whether the effect should be corrected or dismissed in writing.