GATE 2026 MT – Question 35
Two parallel plates with a Newtonian incompressible liquid between them are 2 mm apart. The upper plate is stationary and the lower plate moves with a velocity of 4 m/s. A force per unit area of $5\ \mathrm{N/m^2}$ is applied parallel to the lower plate to maintain its motion. The viscosity of the liquid is ________ $\times10^{-3}\ \mathrm{N\,s/m^2}$. (Rounded off to two decimal places.)
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Correct answer: 2.40 to 2.60
Explanation
For Newtonian Couette flow, $\tau=\eta\Delta u/h$. Rearranging gives $\eta=\tau h/\Delta u=5(0.002)/4=0.0025\ \mathrm{Pa\,s}$.
In the requested units this is $2.50\times10^{-3}\ \mathrm{N\,s/m^2}$, so enter **2.50**.