Question

Your laboratory partner was given the task of measuring the length of a box (approx 5 in) as accurately as possible, using a metre stick graduated in milimeters. 

He supplied you with the following measurements : 

12.65 cm, 12.6 cm, 12.65 cm, 12.655 cm, 126.55 mm, 12 cm. 

a. State which of the measurements you would accept, giving the reason. 

b. Give your reason for rejecting each of the others.

Answer 1

a. The metre stick is graduated in millimetres i.e. 1 mm to 1000 mm, and 1 mm = 0.1 cm. Therefore, if the length is measured in centimetres, the least count of metre stick is 0.1 cm. The results 12.6 cm has the least count of 0.1 cm and is an acceptable result.

b. Since, the least count of metre stick is 0.1 cm or 1 mm, the results such as 12.65 cm, 12.655 cm, 126.55 mm cannot be measured using this stick, and hence, these results are rejected. The result, 12 cm doesn’t include the least count and is rejected.