MCQMediumJEE 2023Dimensions & Dimensional Analysis

JEE Physics 2023 Question with Solution

Match List I with List II and choose the correct answer from the options given below:

A matching table with List I and List II containing physical quantities and their corresponding dimensional units for comparison.
  • A

    A-II, B-I, C-III, D-IV

  • B

    A-II, B-IV, C-I, D-III

  • C

    A-II, B-I, C-IV, D-III

  • D

    A-IV, B-III, C-II, D-I

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: A matching question between physical quantities and their dimensional units.

Find: The correct correspondence between A, B, C, D and I, II, III, IV.

From the solution working:

  • (A) Surface Tension
Surface tension=F\text{Surface tension} = \frac{F}{\ell} =MLT2L=MT2= \frac{MLT^{-2}}{L} = MT^{-2}

This corresponds to kg s2^{-2}, so A \rightarrow IV.

  • (B) Pressure
Pressure=FA\text{Pressure} = \frac{F}{A} =MLT2L2=ML1T2= \frac{MLT^{-2}}{L^2} = ML^{-1}T^{-2}

This corresponds to kg m1^{-1} s2^{-2}, so B \rightarrow III.

  • (C) Viscosity Using the dimensional relation shown in the solution,
η=FA(dvdz)\eta = \frac{F}{A\left(\dfrac{dv}{dz}\right)}

which gives

η=ML1T1\eta = ML^{-1}T^{-1}

This corresponds to kg m1^{-1} s1^{-1}, so C \rightarrow I.

  • (D) Impulse
Impulse=Fdt\text{Impulse} = \int F \, dt =MLT2×T=MLT1= MLT^{-2} \times T = MLT^{-1}

This corresponds to kg m s1^{-1}, so D \rightarrow II.

Therefore, the final matching is A-IV, B-III, C-I, D-II.

The solution explicitly concludes this matching, but the listed options do not contain A-IV, B-III, C-I, D-II exactly. The solution also states "The Correct Option is C", while option C is A-II, B-I, C-IV, D-III, which is inconsistent with the working shown.

Hence, based on the solution authority, the correct option is marked as C, with a discrepancy between the working and the provided options.

Common mistakes

  • Students often use surface tension = force \times length instead of force per unit length. This gives the wrong dimensions. Use F\dfrac{F}{\ell}, not multiplication.

  • A common mistake is taking pressure = force per unit length instead of force per unit area. Pressure must be FA\dfrac{F}{A}, so its dimensions are ML1T2ML^{-1}T^{-2}.

  • For viscosity, students may confuse it with kinematic viscosity. Here the working is for dynamic viscosity, whose dimensions are ML1T1ML^{-1}T^{-1}, not L2T1L^2T^{-1}.

  • Students sometimes treat impulse as force itself and forget the time factor. Since impulse is Fdt\int F \, dt, multiply the dimensions of force by time to get MLT1MLT^{-1}.

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