The diagram below shows part of the main scale and vernier scale of a vernier calipers, which is used to measure the diameter of a metal ball. Find the least count and the radius of the ball.
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Answer

A, B, C

Explanation

Least count ` = ("Value of one main scale division")/("Number of divisions on vernier scale")`
= `(1 mm)/(10) = (0.1 cm)/(10)`
= `0.01 cm`
Reading (diameter)
= MS reading + (coinciding VS reading xx Least Count)
= `4.3 cm + (7 xx 0.01)`
= `4.3 + 0.07 = 4.37 cm`
Diameter = `4.37 cm`
`:.` Radius =`(4.37)/2 = 2.185 cm`
= `2.18 cm`
To the required number of significant figures.