Question

A circular metal plate of radius 5 cm rests on a layer of centre oil 2mm thick whose coefficient of viscosity is 15.5 dyne $c{m}^{-2}s$ . The value of shearing stress when a horizontal force move the plate with a speed of 5 cm/s will be

• A. 387.5 dyne $c{m}^{-2}$
• B. 328 dyne $c{m}^{-2}$
• C. 250 dyne $c{m}^{-2}$
• D. 428 dyne $c{m}^{-2}$

Answer 1

Answer: (A)

Shearing stress $=\eta \times$ strain rate $=\eta .\frac{dv}{dx}=15.5\times \frac{5}{0.2}=387.5dynec{m}^{-2}$