Question

A student measured the length of a rod and wrote it as 3.50 cm. Which instrument did he use to measure it?

• A) A screw gauge having 100 divisions in the circular scale and pitch as 1 mm.
• B) A screw gauge having 50 divisions in the circular scale and pitch as 1 mm.
• C) A meter scale.
• D) A vernier calliper where the 10 divisions in vernier scale matches with 9 division in main scale and main scale has 10 divisions in 1 cm.

Answer 1

Measured length of rod = 3.50 cm
That means least count of the measuring instrument should be 0.01 cm = 0.1 mm
For vernier scale 1 main scale division = 1 mm
And 9 MSD = 10 VSD
Least count = 1 MSD - 1 VSD
= 1 - 0.9 = 0.1 mm