Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Units and Measurements question

2019 · 8 Apr · Shift 2 · Q58
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Units and Measurements
  5. /2019 · 8 Apr · Shift 2 · Q58

Units and Measurements question

2019 · 8 Apr · Shift 2 · Q58

JEE MainPhysicsUnits and MeasurementsMCQ+4 / −1
If surface tension (S), Moment of inertia (I) and Planck's constant (h), were to be taken as the fundamental units, the dimensional formula for linear momentum would be :-
  1. A
    S1/2I1/2h0
  2. B
    S3/2I1/2h0
  3. C
    S1/2I1/2h-1
  4. D
    S1/2I3/2h-1
View written solutionFree

Correct answer: A

  1. Write dimensions of the given fundamental quantities

We take surface tension SSS, moment of inertia III, and Planck's constant hhh as fundamental quantities.

Their dimensions in terms of M,L,TM, L, TM,L,T are:

  • Surface tension: [S]=forcelength=MLT−2L=MT−2[S] = \frac{\text{force}}{\text{length}} = \frac{MLT^{-2}}{L} = MT^{-2}[S]=lengthforce​=LMLT−2​=MT−2

  • Moment of inertia: [I]=ML2[I] = ML^2[I]=ML2

  • Planck's constant: [h]=energy×time=(ML2T−2)⋅T=ML2T−1[h] = \text{energy} \times \text{time} = (ML^2T^{-2})\cdot T = ML^2T^{-1}[h]=energy×time=(ML2T−2)⋅T=ML2T−1

  1. Write dimensions of linear momentum

Linear momentum ppp has dimensions: [p]=MLT−1[p] = MLT^{-1}[p]=MLT−1

  1. Assume momentum in terms of S,I,hS, I, hS,I,h

Let [p]=[S]a[I]b[h]c[p] = [S]^a [I]^b [h]^c[p]=[S]a[I]b[h]c

Substitute the dimensions: MLT−1=(MT−2)a(ML2)b(ML2T−1)cMLT^{-1} = (MT^{-2})^a (ML^2)^b (ML^2T^{-1})^cMLT−1=(MT−2)a(ML2)b(ML2T−1)c

Expanding, MLT−1=Ma+b+cL2b+2cT−2a−cMLT^{-1} = M^{a+b+c} L^{2b+2c} T^{-2a-c}MLT−1=Ma+b+cL2b+2cT−2a−c

  1. Compare powers of M,L,TM, L, TM,L,T

So we get the equations:

  • For MMM: a+b+c=1a+b+c=1a+b+c=1
  • For LLL: 2b+2c=12b+2c=12b+2c=1
  • For TTT: −2a−c=−1-2a-c=-1−2a−c=−1
  1. Solve the equations

From 2b+2c=12b+2c=12b+2c=1 we get b+c=12b+c=\frac{1}{2}b+c=21​

From −2a−c=−1-2a-c=-1−2a−c=−1 we get 2a+c=12a+c=12a+c=1

Now use a+b+c=1a+b+c=1a+b+c=1 Substitute b+c=12b+c=\frac{1}{2}b+c=21​: a+12=1a+\frac{1}{2}=1a+21​=1 a=12a=\frac{1}{2}a=21​

Then from 2a+c=12a+c=12a+c=1 2(12)+c=12\left(\frac{1}{2}\right)+c=12(21​)+c=1 1+c=11+c=11+c=1 c=0c=0c=0

Now b+c=12⇒b=12b+c=\frac{1}{2} \Rightarrow b=\frac{1}{2}b+c=21​⇒b=21​

Thus, [p]=S1/2I1/2h0[p] = S^{1/2} I^{1/2} h^0[p]=S1/2I1/2h0

  1. Match with options

This corresponds to:

Option A: S1/2I1/2h0S^{1/2} I^{1/2} h^0S1/2I1/2h0


Final Answer

S1/2I1/2h0\boxed{S^{1/2} I^{1/2} h^0}S1/2I1/2h0​ So, Option A is correct.

PreviousNext

More from Units and Measurements

  • In the density measurement of a cube, the mass and edge length are measured as (10.00 ± 0.10) kg and (0.10 ± 0.01) m, respectively. The error in the measurement of density is :2019 · MCQ
  • The area of a square is 5.29 cm2. The area of 7 such squares taking into account the significant figures is :-2019 · MCQ
  • A copper wire is stretched to make it 0.5% longer. The percentage change in its electrical resistance if its volume remains unchanged is :2019 · MCQ
  • The pitch and the number of divisions, on the circular scale, for a given screw gauge are 0.5 mm and 100 respectively. When the screw gauge is fully tightened without any object, the zero of its circular scale lies 3 divisions below the…2019 · MCQ
  • Expression for time in terms of G(universal gravitional constant), h (Planck constant) and c (speed of light) is proportional to :2019 · MCQ
  • In the formula X = 5YZ2 , X and Z have dimensions of capacitance and magnetic field, respectively. What are the dimensions of Y in SI units?2019 · MCQ
  • The density of a material in SI units is 128 kg m–3 . In certain units in which the unit of length is 25 cm and the unit of mass is 50 g, the numerical value of density of the material is -2019 · MCQ
  • The diameter and height of a cylinder are measured by a meter scale to be 12.6 ± 0.1 cm and 34.2 ± 0.1 cm, respectively. What will be the value of its volume in appropriate significant figures ?2019 · MCQ