Bob wants to measure the length of the red rectangle above. The ruler has 1 cm tick marks. Bob wants other scientists to have a sense of the likely size of measurement errors. (The uncertainty.) Which reading makes the most sense for him to report? *

1 cm ± 0.05 cm

Explanation:

A ruler is readable to ±0.05 cm. This implies that any measurement taken using the ruler could be uncertain by 0.05 cm above or below the true value.

Hence, ±0.05 cm  is called the uncertainty or the precision of the ruler.

We obtained this from the fact that the meter rule is graduated in units of centimetres (cm). This implies that the smallest scale division is 1 mm. Thus, the uncertainty of the meter rule is given by; Δx = smallest increment/2 = 1mm/2 = 0.5mm = 0.05cm.