Physics

Fluid Mechanics

637 Questions

Fluid mechanics is a core physics topic that evaluates the principles of liquid pressure, buoyancy, density, and viscosity through complex numerical problems. The questions require calculating the volume of submerged objects, understanding hydraulic jumps, and applying fundamental fluid statics principles. It is a highly scoring subject for candidates preparing for technical and engineering competitive exams.

Liquid pressure and depthBuoyancy and densityVolume expansionHydraulic jump calculationsSurface tension mechanics

Fluid Mechanics Questions

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Suppose that a student finds that $24 \ mL$ of a certain liquid weighs $36 \ g$. What is the density of this liquid in SI unit?

  1. $1500 \ kg m^{-3}$
  2. $1200 \ kg m^{-3}$
  3. $1550 \ kg m^{-3}$
  4. $1300 \ kg m^{-3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given, mass of liquid, $m=36g=36\times 10^{-3}kg$;
density of liquid, $\rho=?$
Volume of liquid, $V=24mL=24\times 10^{-3}L$
$=24\times 10^{-3}\times 10^{-3}m^3$
$=24\times 10^{-6}m^3$
Always remember, $1L=10^{-3}m^3=10^3 cm^3$,
Also, $1mL=1cm^3$(also called $1 \ cc$)
Density, $\rho=\displaystyle \frac{Mass}{Volume}=\frac{m}{V}=\frac{36\times 10^{-3}}{24\times 10^{-6}}$
$=1500kg m^{-3}$

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

The densities of three liquids are D, 2D and 3D. What will be the density of the resulting mixture if equal volumes of the three liquids are mixed? 

  1. 6D

  2. 1.4D

  3. 2D

  4. 3D
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

let $V$ be the volume of each liquid then the total volume of the mixture becomes $3V$. 

$\rho = \dfrac{total\ mass}{total\ volume}$

Therefore, the mass of the liquids can be written as:
$m _1=D\times V=DV$
$m _1=2D\times V=2DV$
$m _1=3D\times V=3DV$

the total mass of the liquids is
$M= DV+2DV+3DV=6DV$

Therefore, the density of the mixture is:
$\rho=\dfrac{6DV}{3V}$

$\rho = 2D$

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Two non-mixing liquids of densities $\rho$ and $n \rho ( n >$ 1) are put in a container. The height of each liquids $h$ . A solid cylinder of length $L$ and density $d$ is put in this container. The cylinder floats with its its axis vertical and length $p L ( p < 1 )$ in the denser liquid. The density $d$ is equal to

  1. $\{ 1 + ( n - 1 ) p \} p$
  2. $\{ 1 + ( n + 1 ) p \} p$
  3. $\{ 2 + ( n + 1 ) p \} p$
  4. $\{ 2 - ( n + 1 ) p \} p$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} d=density\, \, of\, \, cylin{ { de } }r \ A=area\, \, of\, \, cross-sectional\, \, of\, \, cylinder \ U\sin  g\, \, law\, \, of\, \, floation, \ weight\, \, of\, \, cylinder=up\, thrust\, \, by\, \, two\, \, liquids \ L\times A\times d\times g \ =n\rho \times \left( { pL\times A } \right) g+\rho \left( { L-pL } \right) Ag \ d=np\rho +\rho \left( { 1-p } \right) =\left( { np+1-p } \right) \rho  \ d=\left{ { 1+\left( { n-1 } \right) p } \right} \rho  \end{array}$

Hence,
option $(A)$ is correct answer.

Multiple choice evs - i our earth and our solar system sunita's experience in space space exploration solar system and sun

Why would it be hard to pour a liquid in a cup kept in space?

  1. The density of liquid increases in space and it can not flow like a liquid

  2. The liquid will freeze in space

  3. The liquid won't fall down as there is no gravity in space

  4. It will stick to the container and hence can not be poured
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As there is no gravity in space, no downward gravitational force acts on the object kept in space.So, the object does not move downwards. When we pour a liquid in a cup kept in space, the liquid do not fall downwards to fill the cup because of zero gravity in the space.

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

Eight spherical droplets, each of radius $'r'$ of a liquid of density $'\phi'$ and surface tension $'T'$ coalesce to form one big drop. If $'s'$ in the specific heat of the liquid. Then the rise in the temperature of the liquid.

  1. $\dfrac {2T}{3r \rho s}$
  2. $\dfrac {3T}{r \rho s}$
  3. $\dfrac {3T}{2r \rho s}$
  4. $\dfrac {T}{r \rho s}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When droplets coalesce, surface energy is released as heat. The change in surface area leads to a temperature rise calculated by equating the change in surface energy to the heat gained by the mass of the liquid.

Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

A biprism arrangement in air is immersed completely in a liquid. The fringe width

  1. remains same

  2. increases

  3. decreases

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\beta =\cfrac { \lambda D }{ d } $

when immersed in a liquid, ${ \lambda  } _{ 1 }=\cfrac { \lambda  }{ \mu  } \ \therefore { \beta  }^{ 1 }=\cfrac { { \lambda  }^{ 1 } }{ d } =\cfrac { \lambda D }{ \mu d } =\cfrac { \beta  }{ \mu  } \ \therefore \beta \quad decreases $

Multiple choice

Forces generated by transportation can create pressures sufficient to lift a xylem sized column of water over

  1. 100 meters high

  2. 110 meters high

  3. 120 meters high

  4. 130 meters high
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transpiration generates negative pressure (tension) in the xylem through water evaporation from leaves. This transpiration pull, combined with water's cohesive properties and adhesion to xylem walls, can theoretically support a water column up to 130 meters high. This explains how tall trees like coastal redwoods transport water to their crowns.

Multiple choice

Can density ever change with size?

  1. Sometimes

  2. Always

  3. Never

  4. Maybe
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Density is an intensive property, meaning it is a characteristic of the substance itself and does not change based on the amount or size of the sample.

Multiple choice

Why do bubbles rise to the top of the water?

  1. Because the bubbles are made of gas

  2. Because the bubbles are more dense than water

  3. Because the air wants to escape the water

  4. Because the bubbles are less dense than the water
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bubbles rise because the gas inside them is significantly less dense than the surrounding liquid water, causing a buoyant force to push them upward.

Multiple choice

ρghA=

  1. buoyant force

  2. sinking force

  3. weight

  4. displacement
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The formula rho*g*h*A represents pressure (rho*g*h) multiplied by area (A), which equals force. In the context of fluids, this is the buoyant force (Archimedes' principle).