Units & Measurements

What you'll learn

Fundamental vs derived quantities, the 7 SI base units, dimensional formulas, and significant figures.

This chapter has

Units & Measurements — solved practice questions

6 JEE Physics questions with step-by-step solutions. Attempt each, then reveal the answer.

1. Q1easy

   What is the SI unit of force?

   • Ajoule
   • Bnewton
   • Cwatt
   • Dpascal
   Show answer & solution

   Correct answer: (B) newton

   Force is measured in newton (N), where 1 N = 1 kg·m/s².

2. Q2medium

   Which of the following is a fundamental (base) quantity?

   • Aforce
   • Bvelocity
   • Cmass
   • Ddensity
   Show answer & solution

   Correct answer: (C) mass

   Mass is a base quantity. Force, velocity and density are all derived from base quantities.

3. Q3medium

   The dimensional formula of velocity is:

   • A[LT⁻¹]
   • B[LT⁻²]
   • C[L²T⁻¹]
   • D[MLT⁻²]
   Show answer & solution

   Correct answer: (A) [LT⁻¹]

   Velocity = displacement/time = L/T = [LT⁻¹].

4. Q4easy

   How many fundamental (base) units are there in the SI system?

   • A5
   • B6
   • C7
   • D9
   Show answer & solution

   Correct answer: (C) 7

   There are 7 SI base units: metre, kilogram, second, ampere, kelvin, mole, candela.

5. Q5hard

   The number of significant figures in 0.00450 is:

   • A2
   • B3
   • C5
   • D6
   Show answer & solution

   Correct answer: (B) 3

   Leading zeros are not significant; 4, 5 and the trailing 0 are → 3 significant figures.

6. Q6medium

   The dimensional formula of acceleration is:

   • A[LT⁻¹]
   • B[LT⁻²]
   • C[MLT⁻²]
   • D[L²T⁻²]
   Show answer & solution

   Correct answer: (B) [LT⁻²]

   Acceleration = velocity/time = (L/T)/T = [LT⁻²].

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