Physics

Fluid Mechanics

673 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 biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

How much pressure would be required to raise water to the top of a $416$ ft. high tree ?

  1. $1$ atm
  2. $13$ atm
  3. $-77$ bars

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

One atmospheric pressure can raise water to a height of more than $32$ feet. So a pressure of about $13$ atmospheres would be required to raise water at the top of a $416$ feet high tree. The tension developed in the xylem sap of trees that are actively transpiring can be measured only indirectly and has been found to be high as $-77$ bars.

Multiple choice evs look, learn and experience brief introduction to atoms of elements elements and atoms introduction of atom

Which of the following changes increases the overall density of the object?

  1. A block of iron is formed into a hollow shape

  2. A submarine fills its ballast tanks with water

  3. A submarine fills its ballast tanks with air

  4. A fish increases the amount of gas in its swim bladder
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a low-density substance is replaced by high-density substance,the overall density increases.Here air which has low density compared to water is replaced.So,the overall density increases while in removing cases overall density decreases.


Option B is correct.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A cylinder of radius R full of liquid of density $\rho$ is rotated about its axis at $\omega$ rad/s. The increase in pressure at the centre of the cylinder will be

  1. $\dfrac{\rho \omega^2 R^2}{2}$
  2. $\dfrac{\rho \omega^2 R}{2}$
  3. $\dfrac{\rho \omega R}{2}$
  4. $\dfrac{\rho^2 \omega^2 R^2}{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a liquid cylinder of density rho rotates at angular speed omega, the pressure variation follows the hydrostatic equation dp/dr = rho omega^2 r. Integrating from the center (r = 0) to the radius R gives the pressure increase as Delta P = rho omega^2 R^2 / 2, making option A correct.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

Equal masses of three liquid are kept in there identical cylindrical vessels $A, B$ and $C$. There densities are $\rho _{A}, \rho _{B}$ and $\rho _{C}$ with $\rho _{A} < \rho _{B} < \rho _{C}$. The force on the base will be

  1. Maximum in vessel $A$
  2. Maximum in vessel $B$
  3. Maximum in vessel $C$

  4. Same in all the three vessel
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Since masses are same,(weight$=mg$) is same for all three.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A liquid column of height $80\ cm$ at $0^{\circ}$ balances the same liquid of height $80.4\ cm$ at $100^{\circ}C. \gamma _{R}$ is

  1. $4\times 10^{-5}/ ^{\circ}C$
  2. $3\times 10^{-5}/ ^{\circ}C$
  3. $5\times 10^{-5}/ ^{\circ}C$
  4. $6\times 10^{-5}/ ^{\circ}C$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The coefficient of real expansion gamma_R = (V2 - V1) / (V1 * deltaT). Using the height change as a proxy for volume change: gamma_R = (80.4 - 80) / (80 * 100) = 0.4 / 8000 = 0.00005 = 5e-5 per degree Celsius.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A block of solid insoluble in water weighs 24 gm in air and 21 gm when completely immersed in water. Its weight when completely immersed in liquid of specific gravity 1.1 is

  1. $20.7 gm$
  2. $27.3 gm$
  3. $24 gm$
  4. $3.3 gm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The loss in weight in water is 24 - 21 = 3 gm, which is the buoyant force. Since the volume is constant, the buoyant force in another liquid is proportional to its specific gravity. Thus, the loss in the new liquid is 3 * 1.1 = 3.3 gm, and the new weight is 24 - 3.3 = 20.7 gm.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A $10cm$ long needle can just rest on the surface of water without wetting, its weight is :

  1. $0.014N$
  2. $0.14N$
  3. $1.4N$
  4. $14N$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Surface Tension of Water $(T) = 0.00072 N/cm $


Here, Weight = Surface tension force = $2Tl$

$\Rightarrow Weight = 2 \times 0.00072 \times 10 = 0.014N$

Therefore, A is correct option.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A smooth rubber ball and a tennis ball some size are placed into two separated containers with the same amount of water in them. 
The ball will move more easily when both of them are spun at the same time?

  1. Smooth rubber ball

  2. Tennis ball

  3. Both will move more easily

  4. They do not move at all
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A smooth rubber ball has less surface friction than a tennis ball, which has a fuzzy texture. When spun in water, the tennis ball experiences more drag due to its surface texture, making the smooth ball move more easily.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation density of a fluid density of fluid density and relative density

A liquid mixture of volume $V$ has two liquids as its ingredients with densities $\alpha  \; and\; \beta $. If the density of the mixture is $\sigma $, then the mass of the first liquid in the mixture is :

  1. $\dfrac{\alpha V[\sigma \beta +1]}{\beta [\alpha +\sigma ]}$
  2. $\dfrac{\alpha V[\sigma -\beta ]}{ [\sigma +\beta]}$
  3. $\dfrac{\alpha V[\beta-\sigma ]}{ \beta-\alpha }$
  4. $\dfrac{\alpha V[1-\sigma\alpha ]}{ \beta[\alpha-\sigma ] }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let mass of liquid with density $\alpha =M _1$
mass of liquid with density $\beta =M _2$
Total volume$=V$
Net density of mixture$=\sigma$
Total mass$=M _1+M _2$
$\Rightarrow V\sigma =M _1+M _2$
$\Rightarrow M _2=V\sigma -M _1$ ......$(1)$

$\left[\because \dfrac{Total \, Mass}{v}=\sigma\right]$

$T=\dfrac{Total \,mass}{Total \, volume}=\dfrac{M _1+M _2}{\dfrac{M _1}{\alpha}+\dfrac{M _2}{\beta}}$ .......$(2)$
sub $(1)$ in $(2)$

$\Rightarrow \sigma =\dfrac{M _1+(v\sigma -M _1)}{\dfrac{M _1}{\alpha}+\left(\dfrac{v\sigma -M _1}{\beta}\right)}$

$\Rightarrow M _1=\dfrac{\alpha V(\beta -\sigma)}{\beta -\alpha}$.
Multiple choice chemistry materials liquid crystals liquid state the liquid state

A liquid of density $1.07\ g/ml$ is filled in the barometer, in place of mercury. What should be the length of liquid column, if another barometer filled with mercury, is measuring $75\ cm$ pressure?

  1. $75\ cm$
  2. $600\ cm$
  3. $9.375\ cm$
  4. $6000\ cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice chemistry materials liquid crystals liquid state the liquid state

A beaker is filled with a liquid of density $\rho $ upto a height pressure on the walls is :

  1. 0
  2. $h \rho g $
  3. $h \rho g/2 $
  4. $2 h \rho g $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The pressure at a depth h in a liquid is rho * g * h. The average pressure on the walls of a container filled to height h is the integral of pressure over the depth, which results in (1/2) * rho * g * h.

Multiple choice landforms on earth and external processes general physical geography general knowledge

If a small raindrop falls through air ______.

  1. its velocity goes on increasing

  2. its velocity goes on decreasing

  3. its velocity goes on increasing for some time and then becomes constant

  4. it falls with constant speed for some time and then its velocity increases
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As a raindrop falls, gravity accelerates it, but air resistance increases with velocity. Eventually, the drag force equals the gravitational force, and the raindrop reaches a constant terminal velocity.

Multiple choice physics superposition of waves-2: stationary (standing) waves: vibrations of air columns determining wavelength and speed of sound resonance tube resonance and sonometer

As an empty vessel is filled with water, its fundamental frequency

  1. Increases

  2. Decreases

  3. Remains the same

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

   An empty vessel with a base is like a closed organ pipe , and fundamental frequency of a closed organ pipe is given by ,

       $n _{1}=v/4l$ ,
where $l=$ length of air column in pipe (height of pipe) ,
  from above we get,    
       $n _{1}\propto 1/l$ ,
when the empty vessel is filled with water , the length of air column $l$ in pipe decreases and therefore fundamental frequency $n _{1}$ increases as length of air column and fundamental frequency are inversely proportional to each other .