Which of the following devices can measure the shortest length? (A) A ruler, (B) Vernier calipers, or (C) a micrometer.
The scale on a ruler is typically in centimeters. But if we look in between the centimeter measurements of the ruler, we should find smaller markings, which denote millimeters instead. This means that the shortest length the ruler can measure is one millimeter. Vernier calipers are much like rulers, except that they have jaws and a scale that allows us to measure in between millimeters. Zooming in, this scale allows us to find measurements as much as up to one twentieth of a millimeter by finding exactly where the lines match up. So the shortest length that Vernier calipers can measure is 0.05 millimeters, or one twentieth of a millimeter.
A micrometer, however, can measure even shorter lengths. When measuring an object with the micrometer, the top scale is full millimeters, and the bottom scale can be used to look at half millimeters. And then there is the scale on the end called the thimble scale. By counting along the full-millimeter scale at the top and the half-millimeter scale at the bottom, these can be combined with the thimble scale which measures one one hundredth of a millimeter. This means that the accuracy of a micrometer is 0.01 millimeters. This is the shortest length that a micrometer can measure and is shorter than either the ruler or the Vernier calipers.
This means that the device that can measure the shortest length is (C), the micrometer, at 0.01 of a millimeter.