College Physics Problem 1.19

(a) If your speedometer has an uncertainty of 2.0 km/h at a speed of 90 km/h, what is the percent uncertainty? (b) If it has the same percent uncertainty when it reads 60 km/ h, what is the range of speeds you could be going?


a) The percent uncertainty is computed as

%uncertainty=frac{2.0  km/h}{90  km/h}=2.2  %


b) The tolerance of the velocity is

delta_{v}=frac{2.2  %}{100  %}times 60  km/h=1  km/h

Therefore, the range of the velocity is 60±1km/h, or that is 59 to 61 km/h.