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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: =...

Determine if the following equation is dimensionally correct:
ν=12πmglI\nu = \dfrac{1}{2 \pi} \sqrt{\dfrac{mgl}{I}}
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 [T−2][T^{-2}].
  2. BThe equation is dimensionally correct.
  3. CThe equation is dimensionally incorrect, as the right side is dimensionless.
  4. DThe equation is dimensionally incorrect, as the right side has dimensions of [ML2T−1][M L^2 T^{-1}].

Correct answer

B. The equation is dimensionally correct.

Step-by-step solution

Dimensions of the left hand side (LHS):
[ν]=[T−1][\nu] = [T^{-1}]

Dimensions of the terms on the right hand side (RHS):
[m]=[M][m] = [M]
[g]=[LT−2][g] = [L T^{-2}]
[l]=[L][l] = [L]
[I]=[ML2][I] = [M L^2]

Substituting these into the expression under the square root:
\left[\dfrac{mgl}{I}\right] = \dfrac{[M][L T^{-2}][L]}{[M L^2]} = [T^{-2}]<br><br>TakingthesquarerootfortheRHS:<br>[mglI]=[T−2]=[T−1]<br><br>Taking the square root for the RHS:<br>\left[\sqrt{\dfrac{mgl}{I}}\right] = \sqrt{[T^{-2}]} = [T^{-1}]

Since the dimensions of the LHS and RHS are equal, the equation is dimensionally correct.
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