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The least count of the main scale of a vernier callipers is 1 mm. Its vernier scale is divided into 10 divisions and coincide with 9 divisions of the main scale. When jaws are touching each other, the 7th division of vernier scale coincides with a division of main scale and the zero of vernier scale is lying right side of the zero of main scale. When this vernier is used to measure length of a cylinder the zero of the vernier scale is between 3.1 cm and 3.2 cm and 4th VSD coincides with a main scale division. The length of the cylinder is : (VSD is vernier scale division) (1) 3.21 cm (2) 2.99 cm (3) 3.2 cm (4) 3.07 cm
- 3.21 cm
- 2.99 cm
- 3.2 cm
- 3.07 cm
Correct answer: 3.2 cm
Solution
The length of the cylinder is determined by adding the main scale reading (3.2 cm) to the value of the coinciding vernier scale division (4th VSD), which corresponds to 0.01 cm. However, since the zero of the vernier scale is to the right of the main scale zero, the measurement does not include the additional value from the vernier, confirming the length as 3.2 cm.
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