Machine-translated by Google. Questions are authored in English.
Top

Discussion

The dimension of X in the equation, \(F = 6\pi\eta X\) is
( F - Force; η -Coefficient of viscosity)

  • A.\(M^{0}L^{2}T^{-1}\)
  • B.\(ML^{2}T^{-2}\)
  • C.\(M^{0}L^{2}T^{-2}\)
  • D.\(M^{0}L^{3}T^{-2}\)
  • E.\(ML^{2}T^{-1}\)

Answer: A

The dimension of X is \(M^{0}L^{2}T^{-1}\).

Rearrange for X; the number \(6\pi\) is dimensionless. Force is \(MLT^{-2}\), and the coefficient of viscosity (from \(F = \eta A\frac{dv}{dx}\)) is \(ML^{-1}T^{-1}\).

\[ \begin{aligned} [X] &= \frac{[F]}{[\eta]} = \frac{MLT^{-2}}{ML^{-1}T^{-1}} \\ &= M^{0}L^{2}T^{-1} \end{aligned} \]

So X has the dimensions of area per second (in Stokes' law \(F = 6\pi\eta rv\), X stands for the product rv). \(ML^{2}T^{-2}\) is energy, \(ML^{2}T^{-1}\) is angular momentum, and the other two have the wrong power of T or L.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.