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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Introduction to Physics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Introduction to Physics

Determine if the following equation is dimensionally correct: h =...

Determine if the following equation is dimensionally correct:
h=2Scos⁡θρrgh = \dfrac{2 S \cos\theta}{\rho r g}
where h=h = height, S=S = surface tension, ρ=\rho = density, P=P = pressure, V=V = volume, η=\eta = coefficient of viscosity, ν=\nu = frequency and I=I = moment of inertia.

Options

  1. AThe equation is dimensionally incorrect, as the right side has dimensions of [L2][L^2].
  2. BThe equation is dimensionally incorrect, as the right side has dimensions of [L−1][L^{-1}].
  3. CThe equation is dimensionally incorrect, as the right side has dimensions of [MLT−2][M L T^{-2}].
  4. DThe equation is dimensionally correct.

Correct answer

D. The equation is dimensionally correct.

Step-by-step solution

Dimensions of the left-hand side:

[h]=[L][h] = [L]

Dimensions of the quantities on the right-hand side:

[S]=[MT−2][S] = [M T^{-2}]

[cos⁡θ]=[M0L0T0][\cos\theta] = [M^0 L^0 T^0]

[ρ]=[ML−3][\rho] = [M L^{-3}]

[r]=[L][r] = [L]

[g]=[LT−2][g] = [L T^{-2}]

Substituting these dimensions into the right-hand side:

RHS =[MT−2][ML−3][L][LT−2]= \dfrac{[M T^{-2}]}{[M L^{-3}] [L] [L T^{-2}]}

RHS =[MT−2][ML−1T−2]= \dfrac{[M T^{-2}]}{[M L^{-1} T^{-2}]}

RHS =[L]= [L]

Since the dimensions of the left-hand side equal the dimensions of the right-hand side, the equation is dimensionally correct.
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