(i) Define fractional (relative) uncertainty of a physical quantity. (ii) A student…
PHYSICS · Subjective · A Level · Physics · Measurements and their errors · Measurements and their errors
Problem
(i) Define fractional (relative) uncertainty of a physical quantity.
(ii) A student measures two lengths required to calculate the area of a narrow strip. She records
length x=15.2cm with an absolute uncertainty of ±0.1cm, and
breadth y=0.36cm with an absolute uncertainty of ±0.01cm. Calculate the fractional uncertainty for each measurement.
(iii) Using your results of part (ii), explain quantitatively why quoting only absolute uncertainties would give a misleading impression of the precision of the two measurements when they are later multiplied to obtain the area. Support your explanation with suitable numerical comparison.