Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity) : (d) the number of strands of hair on your head
Area of the head surface carrying hair =A With the help of a screw gauge, the diameter and hence, the radius of a hair can be determined. Let it be r. Area of one hair = r 2 Number of strands of hair = Total surface area / Area of one hair = r 2 A
