A screw gauge has a pitch of 1 mm and 100 divisions on its circular scale. The least count of this instrument is: MCQ with Answer and Explanation

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A screw gauge has a pitch of 1 mm and 100 divisions on its circular scale. The least count of this instrument is:

A. 0.1 mm

B. 0.01 mm

C. 0.001 mm

D. 0.0001 mm

Answer: Option B

Solution (By JKSSB Mock Tests)

Least count of screw gauge = Pitch / Number of circular scale divisions. Given pitch = 1 mm, divisions = 100, so LC = 1 mm / 100 = 0.01 mm. This represents the smallest measurement the instrument can accurately detect. Screw gauges measure small dimensions like wire diameter with high precision. Memory tip: Least count formula is universal for vernier and screw instruments: value per division on main scale divided by total circular divisions. This concept is frequently tested in practical physics sections of competitive exams.

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In a perfectly elastic collision between two bodies, which of the following physical quantities are conserved?

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Correct Answer: Option C

Explanation:
In any collision (elastic or inelastic), the total linear momentum is always conserved, provided no external forces act on the system. However, a perfectly elastic collision is specifically defined as one in which there is absolutely no loss of kinetic energy. Therefore, both total linear momentum and total kinetic energy are conserved.

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A. Scattering

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Correct Answer: Option D

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Dispersion happens because refractive index varies with wavelength. Prism, rainbow. Scattering is Tyndall effect (blue sky). Polarisation restricts vibrations.

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Correct Answer: Option C

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