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 physics measurements and units measuring mass measurement of mass measuring instruments

An object hangs from a spring balance. The balance indicates  $30 { N }$  in air and  $20 { N }$  when the object is submerged-in.water. What does the balance indicate when the object is submerged in a liquid. with a density that is half that of water ?

  1. $20 N$
  2. $25 N$
  3. $30 N$
  4. $35 N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The buoyant force is proportional to the density of the liquid. In water, the loss is 30 - 20 = 10 N. In a liquid with half the density of water, the buoyant force is half, which is 5 N. The reading is 30 - 5 = 25 N.

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

The top of liquids have a flat surface because _____________.

  1. pressure

  2. temperature

  3. gravity

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

The top of a liquid will usually have a flat surface. That flat surface is the result of gravity pulling on the liquid molecules. If you put an ice cube (solid) into the cup, it will sit there and not change shape. As the cube warms and melts, the liquid water will fill the bottom of the cup and have a flat surface on top.

Multiple choice chemistry the particle theory diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

Liquids occupy the entire volume of the container in which they are placed.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Liquids do not occupy the entire volume of the container in which they are placed. They occupy only the volume equal to their volume in the container. This is because there is a strong intermolecular force of attraction present between the molecules of the liquid.

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

Two vertical parallel glass plates are partially submerged in water. The distance between the plates is $d = 0.10 mm$, and their width is $l  = 12 cm$. Assuming that the water between the plates does not reach the upper edges of the plates and that the wetting is complete, find the force of their mutual attraction.

  1. $17N$
  2. $13N$
  3. $10$
  4. $19N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The force of attraction between two plates submerged in liquid is F = 2 * gamma * l * cos(theta) / d. Assuming water (gamma = 0.073 N/m), l = 0.12 m, d = 0.0001 m, and complete wetting (theta = 0), F = 2 * 0.073 * 0.12 / 0.0001 = 175.2 N. This seems to be a specific physics problem where 13N might be the intended answer based on different constants or approximations.

Multiple choice

The buoyant force on a object in a fluid is = to the weight of the fluid displace.

  1. Boyles Law

  2. Charles's Law

  3. Bernoulli's Principle

  4. Archimedes' Principle
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Archimedes' Principle states that the buoyant force on an immersed object equals the weight of fluid displaced. Boyle's Law relates pressure and volume, Charles's Law relates temperature and volume, and Bernoulli's Principle relates fluid speed and pressure.

Multiple choice physics floatation pressure in fluids pressure in liquids introduction to pressure
The magnitude of buoyant force acting on an object immersed in a liquid depends on

  1. Volume of object immersed in the liquid.

  2. Density of the liquid.

  3. Both A and B

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Archimedes Principle, the magnitude of buoyant force experienced is equal to the weight of liquid displaced by it by being placed in it.

Hence $B=V _{immersed}\rho g$
Hence $B$ depends both on $V _{immersed}$ and $\rho$.
Correct answer is option C.

Multiple choice physics forces and matter pressure in fluids pressure in liquids introduction to pressure

The pressure in a water pipe on the second floor of a building is 60,000 Pa, and on the third floor it is 30,000 Pa. Find the height of the second floor. (Density of water $=1000 kg m^{-3}, g=10 m s^{-2})$.

  1. 3 m

  2. 4 m

  3. 5 m

  4. 6 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Second floor :
$P _1=60,000 Pa, g=10 ms^{-2}$
$P _1=h _1dg$


$60,000=h _1\times 1000\times 10$

$h _1=\dfrac {60,000}{1000\times 10}=6 m$

[where $h _1=$ height of water tank above second floor]

Third floor :
$P _2=30,000 Pa, g=10 m s^{-2}$,


$\therefore 30,000=h _2\times 1000\times 19$

$\Rightarrow h _2=\dfrac {30000}{1000\times 10}=3 m$

[where $h _2=$ height of water tank above first floor]

$\therefore $ height of the second floor
$=h _1-h _2=6m-3m=3m$

Multiple choice physics forces and matter pressure in fluids pressure in liquids introduction to pressure

The pressure in water pipe at the ground floor of a building is 120000 Pa, where as the pressure on a third floor is 30000 Pa. What is the height of third floor?
[Take $g=10 m s^{-2}$, density of water $=1000 kg m^{-3}]$.

  1. 9 m

  2. 10 m

  3. 11 m

  4. 12 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Difference in pressure of water at ground floor and third floor
$=(120000-300000)=900000 Pa$
Density of water $=1000 kg m^{-3}$
Let 'h' be the height third floor.
$P=hdg$
$h=\dfrac {p}{dg}=\dfrac {90000}{1000\times 10}=9m$.

Multiple choice physics forces and matter pressure in fluids pressure in liquids introduction to pressure

The pressure of water on the ground floor is 50000 Pa and at the first floor is 20000 Pa. Find the height of the first floor. Take density of water is $10^3 kg m^{-3}$ and $g=10 ms^{-2}$

  1. 2 m

  2. 3 m

  3. 4 m

  4. 5 m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pressure on the ground floor $=$ Pressure on the first floor + hdg
$\Rightarrow 50000=20000+hdg$
$\Rightarrow 50000=20000+h\times 10^3\times 10$
$\Rightarrow h\times 10^4=50000-20000$
$\Rightarrow h=\frac {30000}{10000}m$
$\Rightarrow height=3 m.$

Multiple choice physics forces and matter pressure in fluids pressure in liquids introduction to pressure

Calculate the pressure exerted by 0.8 m vertical length of alcohol of density $0.8 g cm^{-3}$. (Acceleration due to gravity $(g)=10 m s^{-2})$.

  1. 3200 Pa

  2. 6400 Pa

  3. 800 Pa

  4. 5000 Pa
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Vertical length of the alcohol column
$(h)=0.8 m$
Density of alcohol $(d)=0.8 g cm^{-3}$
$=0.8\times 1000=800 kg m^{-3}$
$[\therefore 1 g cm^{-3}=1000 kg m^{-3}]$
$Pressure = hdg$
$=0.8\times 800\times 10$
$=6400 Pa$
Therefore, pressure exerted by the alcohol column is 6400 Pa.