Question

The force $F$ on a sphere of radius $a$ , moving in a medium with velocity $v$ , is given by $F = 6 \pi \eta a v$ . The dimensions of $\eta$ are

• A. $\left[ML^{- 1} T^{- 1}\right]$
• B. $\left[MT^{- 1}\right]$
• C. $\left[MLT^{- 2}\right]$
• D. $\left[ML^{- 3}\right]$

Answer 1

Answer: (A)

$\eta=\frac{F}{a v}=\frac{\left[\right. MLT^{- 2} \left]\right.}{\left[\right. L \left]\right. \left[\right. LT^{- 1} \left]\right.}=\left[ML^{- 1} T^{- 1}\right]$