List of practice Questions

A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair ?

The mass of a box measured by a grocer’s balance is 2.30 kg. Two gold pieces of masses 20.15 \(\text g\) and 20.17 \(\text g\) are added to the box. What is 

1. the total mass of the box, 
2. the difference in the masses of the pieces to correct significant figures ?