Question

A student wishes to measure a distance of about 10 cm to a precision of 0.01 cm. Which measuring instrument should be used?
A. Metre rule
B. Micrometer
C. Tape meter
D. Vernier callipers

Answer 1

Hint: In this question we are asked to select the instrument to measure a certain reading with a precision of 0.01 cm. Therefore, we will discuss the given options and their precision in taking the reading. We will discuss which is the suitable tool for measuring with accuracy of 0.01 cm.

Complete answer:
It is given that the student wishes to measure a 10 cm distance with a precision of 0.01 cm i.e. 0.1 mm. The first instrument given to us is the meter rule. Now we know that the smallest reading on a meter rule is 1 cm. Therefore, the required precision can not be achieved if the meter rule is used for measurement.
Now, the second option is the micrometer. As we know, a micrometer is a high precision instrument. The precision of the micrometer is 0.005 mm. Therefore, the required precision is lower than precision of the instrument. So, it is also not a good selection.
The tape meter has the minimum reading of 1 mm. The precision of 0.1mm can not be obtained through a tape meter. Now, the last option is vernier calliper. The precision of the vernier calliper is 0.1mm. The minimum reading on a vernier calliper is 0.1 mm. Therefore, vernier calliper is a suitable instrument to measure 10 cm with precision of 0.01 cm.
Therefore, the correct answer is option D.

Note: The vernier calliper is an instrument used to measure the dimensions of the objects. The dimensions such as the outer radius and inner radius of a cylinder, or the radius of a sphere, thickness of rod, etc can be measured. To avoid instrument error while measuring with a vernier calliper, the least count of the instrument is noted.