L2 Combining Measurements
Completion requirements
Unit B: Measurement
Combining Measurements
When two or more measurements are added or subtracted, the uncertainty must be taken into account. The precision and uncertainty must have the same units before two measurements can be combined.
Step 1: Add or subtract the measurements.
Step 2: Add the uncertainties.
Note: Uncertainties must always be added together since the uncertainty increases with the number of measurements.
Michael would like to put two boxes on a shelf that is 12 inches from the ceiling. One box is 6 inches high and the other is 5 inches high. Can Michael put these two boxes on the shelf without touching the ceiling?
Box 1 would have a height of 6 in ± 0.5 in and box 2 would have a height of 5 in ± 0.5 in. Together, their height would be 6 in + 5 in = 11 in with an uncertainty of 0.5 in + 0.5 in = 1 in. Therefore, the height of the boxes in between 10
in and 12 in. The boxes could fit, but it is not a guarantee.