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← JEE Main 2015 · 10 Apr · Shift 1
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JEE Main 2015 · 10 Apr · Shift 1, Physics question 30

Diameter of a steel ball is measured using a Vernier callipers which has divisions of 0.1 cm on its main scale (MS) and 10 divisions of its vernier scale (VS) match 9 divisions on the main scale. Three such measurements for a ball are given as :

S.No. MS (cm) VS divisions
1. 0.5 8
2. 0.5 4
3. 0.5 6

If the zero error is −0.03 cm, then mean corrected diameter is :

Choose one option
Answer and worked solution

Official answer: B

Least count: 0.1−0.09=0.010.1-0.09=0.01 cm. Readings 0.580.58, 0.540.54 and 0.560.56 cm, mean 0.560.56 cm. Correcting the zero error of −0.03-0.03:
0.56−(−0.03)=0.59 cm.0.56-(-0.03)=0.59\text{ cm}.