Viscosity and Newtonian Law

Q. Calculate the kinematic viscosity (stokes) of the fluid if the dynamic viscosity of fluid is 0.5 poise and specific gravity is 0.4?

1. $0.95$
2. $1$
3. $1.25$
4. $1.5$

Q. Poise has the unit of

1. Dyne-cm/$s^2$
2. Dyne-cm/s
3. Dyne-s/cm
4. Dyne-s/c$m^2$

Q.

Why is the oil used to calm sea waves?

Q. What is the unit of kinematic viscosity?

1. Poise
2. N-sec/m${}^2$
3. Stokes
4. Dimensionless

Q. A fluid is said to be Newtonian fluid when the shear stress is

1. directly proportional to the velocity gradient
2. inversely proportional to the velocity gradient
3. independent of the velocity gradient
4. none of these

Q. A flat plate of 0.15 $m^2$ is pulled at 20 cm/s relative to another plate, fixed at a distance of 0.02 cm from it with a fluid having $\mu$ = 0.0014 N-s/$m^2$ separating them. What is the power required to maintain the motion?

1. 0.014 W
2. 0.021 W
3. 0.035 W
4. 0.042 W

Q. A fluid is one which can be defined as a substance that

1. has that same shear stress at all points
2. can deform indefinitely under the action of the smallest shear force
   
3. has the small shear stress in all directions
4. is practically incompressible

Q. The SI unit of kinematic viscosity $\nu$ is

1. $m^2/s$
2. kg/ms
3. $m/s^2$
4. $m^3/s^2$

Q. The velocity distribution in a laminar flow adjacent to a solid wall is given by u=3.0 sin (5$\pi$y). The viscosity of the fluid is 5 poise. What is the shear stress at a section (i) y= 0.05; (ii) y= 0.12 m?

1. 16.7 N/$m^2$ and 6.1 N/$m^2$
2. 33.4 N/$m^2$ and zero
3. 16.7 N/$m^2$ and 12.3 N/$m^2$
4. 16.7 N/$m^2$ and zero

Q. The velocity distribution for flow over a plate is given by $u=0.5y-y^2$ where 'u' is the velocity in m/s at a distance 'y' meter above the plate. If the dynamic viscosity of the fluid $0.9N-s/m^2$, then what is the shear stress at 0.20 m from the boundary ?

1. 0.9 N/$m^2$
2. 1.9 N/$m^2$
3. 2.25 N/$m^2$
4. 0.09 N/$m^2$

Q. A circular disc of radius R is kept at small height above a fixed bed by means of a layer of oil of viscosity $\mu$. If the disc is rotated at an angular velocity $\omega$ , what is the expression for viscous torque on the disc ?

1. $\frac{\pi \mu \omega }{h}{R}^4$
2. $\frac{\pi \mu \omega R^4}{4h}$
3. $\frac{\pi \mu \omega R^4}{2h}$
4. Zero

Q. For a Newtonian fluid

1. shear stress is proportional to shear strain
2. rate of shear stress is proportional to shear strain
3. shear stress is proportional to rate of shear strain
4. rate of shear stress is proportional to rate of shear strain

Q. Fluids for which apparent viscosity decreases with velocity gradient are called

1. Dilatant
2. Rheopectic
3. Bingham plastic
4. Pseudo plastic

Q.

Longitudinal strain is possible in ____

Q. The variation of velocity gradient and shear stress is tabulated as under:
$\begin{array}{ccccc}\frac{du}{dy}\left(rad/sec\right)& 0& 0.2& 0.4& 0.6\\ \tau \left(kPa\right)& 4& 8& 11& 13\end{array}$

the fluid may be classified as:

1. Bingham plastic
2. Pseudoplastic
3. Rheopectic
4. Thixotropic

Q. The unit of dynamic viscosity of a fluid is

1. $m^2/s$
2. $Ns/m^2$
3. $Pa{s}^2/m^2$
4. $kg{s}^2/m^2$

Q. The dimension for kinematic viscosity is

1. $\frac{L}{MT}$
2. $\frac{L}{T^2}$
3. $\frac{L^2}{T}$
4. $\frac{ML}{T}$

Q.

A motor boat is travelling with a speed of $3.0m{s}^{-1}$. If the force on it due to water flow is $500N$, the power of the boat is

1. $150kW$

2. $15kW$

3. $1.5kW$

4. $150W$