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⚛️ Physics  ·  Units and Measurements  ·  NEET & JEE

In the formula for the viscous force F = 6πηrv (Stokes' law), η is coefficient of viscosity, r is radius, and v is velocity. If η is found by measuring F, r, and v with relative errors of 2%, 1%, and 2% respectively, the maximum relative error in η is:

Answer: 5%.

  • A 3%
  • B 5%
  • C 1%
  • D 9%

Correct answer: B. 5%

Explanation: Since η = F/(6πrv), the relative errors in F, r, and v simply add: 2% + 1% + 2% = 5%.

The 7 SI Base UnitsLengthmetre (m)fundamentalMasskilogram (kg)Timesecond (s)Electric Currentampere (A)Temperaturekelvin (K)Amount ofSubstancemole (mol)LuminousIntensitycandela (cd)Every other physical quantity is derived by combining powers of these 7 base units

The 7 SI base units. All derived units (newton, joule, watt, volt, etc.) can be expressed as combinations of these 7 fundamental units raised to various powers.

Concept context

SI base units, dimensional analysis, significant figures, and error propagation. The toolkit every physics calculation relies on.

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