Answer to Question #210388 in Physics for Alpha

Question

If the least count of scale is 0.1cm then is it possible that we can measure lenght up to two decimal places with that scale?

Answer 1

On the ruler in figure 1, the closest marks are 0.1 cm apart, so you can estimate to the hundredths place, 0.01 cm. However, when looking at a metric ruler in the real world, the smallest marks (i.e. millimeter marks, mm) are so close that it is all we can do just to determine that the dotted line is between two of them—about half way. Therefore, your best estimate of the position of the dotted line is 6.65 centimeters. We can say that the measuring instrument is readable to ±0.05 cm. The ±0.05 cm means that your measurement may be off by as much as 0.05 cm above or below its true value. This value is called the uncertainty or the precision of the instrument.