Tag: viscosity

Questions Related to viscosity

If the shearing stress between the horizontal layers of water in a river is $1.5 mN/ m^{2}$ and $\eta  _{water}= 1\times10^{-3}Pa-s$ , The velocity gradient is:

viscosity option b: engineering physics properties of matter physics

  1. $1.5$

  2. $3$

  3. $0.7$

  4. $1$

Show answer
Correct Option: A
Explanation:

Shearing stress  $=\eta \dfrac{dv}{dy}=1.5 \times 10^{-3} N /m^{2}$


$\Rightarrow 1 \times 10^{-3} \dfrac{dv}{dy}=1.5 \times 10^{-3}$

$\Rightarrow \dfrac{dv}{dy}=1.5 \ s^{-1}$

An air bubble of radius $1 mm$ moves up with uniform velocity of $0.109ms^{-1}$ in a liquid column of density $14.7 \times 10^{3} kg/m^{3}$, then coefficient of viscosity will be ($g = 10ms^{-2}$)

viscosity option b: engineering physics properties of matter physics

  1. $1.3 Pa- s$

  2. $300 Pa -s$

  3. $15 Pa- s$

  4. $150 Pa- s$

Show answer
Correct Option: A
Explanation:

If the bubble is moving up with uniform velocity, the frictional force acting downwards is equal to the buoyant force acting upwards.

$\implies V\rho g=6\pi\eta rv$
$\implies \eta=\dfrac{V\rho g}{6\pi rv}$
$=0.3Pa.s$

Match List I with List II and select the correct answer using the codes given below the lists :

List I List II
p. Boltzmann constant 1. $[ML^2T^{-1}]$
q. Coefficient of viscosity 2. $[ML^{-1}T^{-1}]$
r. Planck constant 3. $[MLT^{-3}K^{-1}]$
s. Thermal conductivity 4. $[ML^2T^{-2}K^{-1}]$
viscosity option b: engineering physics properties of matter physics

  1. P - 3, Q - 1, R - 2, S - 4

  2. P - 3, Q - 2, R - 1, S - 4

  3. P - 4, Q - 2, R - 1, S - 3

  4. P - 4, Q - 1, R - 2, S - 3

Show answer
Correct Option: C
Explanation:

$c. p \rightarrow (4); q \rightarrow (2); r \rightarrow (1); s \rightarrow (3)$

The space between two large horizontal metal plates 6 cm apart, is filled with 
liquid of viscosity 0.8 $N/m^2.$ A thin plate of surface area 0.01 $m^2$ is moved  parallel to the length of the plate such that the plate is at a distance of 2 m  from one of the plates and 4 cm from the other. If the plate moves with a  constant speed of 1 m $s^{-1}$, then

viscosity option b: engineering physics properties of matter physics

  1. the layer of the fluid, which is having the maximum velocity, is lying mid-way between the plates

  2. the layers of the fluid, which is in contact with the moving plate, is having the maximum velocity

  3. the layer of the fluid, which is in Contact with the moving plate and is on the side of farther plate, is moving with the maximum velocity

  4. the layer of the fluid, which is in contact with the moving plant and is on the Side of nearer plate, is moving with the maximum velocity

Show answer
Correct Option: B
Explanation:

The profile of the velocity of fluid as shown in the figure The velocity of the layer of fluid ,which in contact with metal plates (fixed), is zero. As we move towards the centre from either plate the velocity of the layer of fluid increases and it becomes maximum at the location of moving plate. This maximum value is same as that of the velocity of plate

A solid ball of density half that of water falls freely under gravity from a height of 19.6 m and then enters the water. Up to what depth will the ball go? How much time will it take to come again to the water surface. Neglect air resistance and viscosity effects in water. ($
g=9.8 \mathrm{ms}^{-2}
$)

viscosity option b: engineering physics properties of matter physics

  1. 4 s

  2. 8 s

  3. 6 s

  4. 2 s

Show answer
Correct Option: A

A spherical ball of radius $3\times 10^{-4}\ m$ and density $10^{4}\ kg\ m^{-3}$ falls freely under gravity through a distance $h$ before entering a tank of water. If after entering the water, the velocity of the ball does not change, then the value of $h$ is (Given, $viscosity >of> water=9.8\times 10^{-6}\ Nsm^{-2}$ and $\rho _{water}=10^{3}\ kgm^{-3}$)

viscosity option b: engineering physics properties of matter physics

  1. $1650\ m$

  2. $165\ m$

  3. $1050\ m$

  4. $105\ m$

Show answer
Correct Option: A