Mechanical Properties Of Fluids CBSE Questions & Answers

Mechanical Properties Of Fluids

This is Physics Class 11 Mechanical Properties of Fluids CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
According to Bernoulli’s equation for a varying cross-section pipe carrying incompressible liquid, pressure p, density \(\rho \) velocity v and height h at a place where acceleration due to gravity is g
  • A
    \(P + {1 \over 2}\rho {v^2} + \rho gh = constant\)
    Correct
  • B
    \(P + {1 \over 2}\rho {v^2} + 2\rho gh = constant\)
  • C
    \(P + {1 \over 3}\rho {v^2} + \rho gh = constant\)
  • D
    \(P + \rho {v^2} + \rho gh = constant\)
2
If a ball is spinning in an airflow it
  • A
    develops pressure difference between the lower and upper faces due differences in the height of air giving rise to lift
  • B
    develops pressure difference between the lower and upper faces due differences in the velocities of air giving rise to lift
    Correct
  • C
    develops pressure difference between the lower and upper faces due differences in the viscosity of air giving rise to lift
  • D
    develops pressure difference between the lower and upper faces due differences in the density of air giving rise to lift
3
The lift on an aircraft wing arises because of
  • A
    velocity increase and pressure decrease on the lower side of the wing
  • B
    velocity decrease and pressure decrease on the lower side of the wing
  • C
    velocity increase and pressure increase on the lower side of the wing
  • D
    velocity decrease and pressure increase on the lower side of the wing
    Correct
4
The coefficient of viscosity for a fluid is defined
  • A
    as the ratio of shearing stress to the flow rate
  • B
    as the ratio of compressive stress to the strain rate
  • C
    as the ratio of shearing stress to the strain rate
    Correct
  • D
    as the ratio of tensile stress to the strain rate
5
According to Stokes’ law if \(\eta \) is the coefficient of viscosity, 'a' the radius of the sphere and it is moving with a velocity v the viscous drag force F is given by
  • A
    F = 6\(\pi \eta \)a
  • B
    F = 6\(\pi \)av
    Correct
  • C
    F = 2\(\pi \eta \)av
  • D
    F = 6\(\pi \)av
6
If \(\rho \) is the density of the fluid flowing with a speed v, d stands for the dimension of the pipe, and \(\eta \) is the viscosity of the fluid Reynolds number \({{\rm{R}}_{\rm{e}}}\) is given by
  • A
    \({{\rm{R}}_{\rm{e}}}\) = \(\rho {\rm{d}}/\eta \)
  • B
    \({{\rm{R}}_{\rm{e}}}\) = \(\rho {\rm{v}}/\eta \)
  • C
    \({{\rm{R}}_{\rm{e}}}\) = \(\rho {\rm{vd}}/\eta \)
    Correct
  • D
    \({{\rm{R}}_{\rm{e}}}\) = \(\rho {\rm{vd}}\eta \)
7
The molecules on the surface,
  • A
    the unbalanced attractions cause the surface to resist being stretched
    Correct
  • B
    none of these
  • C
    the unbalanced attractions cause the surface to stretch more
  • D
    the balanced attractions cause the surface to resist being stretched
8
Water drops are spherical because of
  • A
    viscosity
  • B
    surface tension
    Correct
  • C
    low shear strain
  • D
    elasticity
9
If a film of width l is stretched in the longitudinal direction a distance d by force F, surface tension is given by
  • A
    S = F/3l
  • B
    S = F/l
  • C
    S = F/4l
  • D
    S = F/2l
    Correct
10
Capillary Rise of water is explained by
  • A
    elasticity
  • B
    surface tension
    Correct
  • C
    low shear strain
  • D
    viscosity
11
An iron needle floats on the surface of water. This phenomenon is attributed to
  • A
    surface tension
    Correct
  • B
    gravitational forces
  • C
    Viscosity
  • D
    up thrust of liquid
12
The excess pressure across the surface of a soap bubble of radius r(with σ as the surface tension of soap solution)is
  • A
    4 \(\sigma \) / r
    Correct
  • B
    2 \(\sigma \) / r
  • C
    8 \(\sigma \) / r
  • D
    \(\sigma \) / r
13
Two soap bubbles are blown simultaneously .In the first soap bubble, the excess pressure is 4 times of second soap bubble. The ratio of radii of first to second soap bubble is
  • A
    it is 2:1
  • B
    it is 1:4
    Correct
  • C
    it is 4:1
  • D
    it is 1:2
14
A drop of oil is placed on the surface of water. Which of the following statements is correct?
  • A
    it will spread as a thin layer
    Correct
  • B
    it will float as a distorted drop on the water surface
  • C
    it will partly changed to spherical droplets and partly as thin film
  • D
    it will remain on it as a sphere
15
Two small drops of mercury, each of radius r, form a single large drop. The ratio of surface energy before and after this change is
  • A
    it is 1:2
  • B
    it is 1:2\(^{{\rm{1}}/{\rm{3}}}\)
    Correct
  • C
    t is 2:1
  • D
    2\(^{{\rm{1}}/{\rm{3}}}\):1