Question

A glass plate of surface area 1 $m^2$placed on a layer of turpentine of thickness 2 mm. If the coefficient of viscosity of turpentine 0.00149 N sm^–2 The force to be applied to move the plate horizontally with a velocity of $0.1m{s}^{-1}$ is

• A. 745 N
• B. 74.5 N
• C. 7.45 N
• D. 0.0745 N

Answer 1

The correct option is

B

0.0745 N

$F=\eta A\left(\frac{dv}{dx}\right)$

$F=\left(0.00149\right)\left(1\right)\left(\frac{0.1}{2\times {10}^{-3}}\right)$

$F=0.0745$ N