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 properties of natural resources conservation of water and recycling properties of water structure and properties of water

Ice has density less that $1\ g \ cm^{-3}$.

  1. True

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

The density of ice is less than the density of water i.e., $1$ $g/cm^3$ due to its cage like structure of hydrogen bonds. The orientation of hydrogen bonds cause the molecules to push further apart which lowers its density. 

Multiple choice biology movement in and out of the cell transport of molecules osmosis and plasmolysis plant water relation

Choose the correct answers from the alternatives given :
The osmotic pressure of pure water is

  1. 0

  2. 0.1

  3. 1

  4. 10
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Osmotic pressure is the minimum pressure applied to prevent the inward flow of solvent molecules from a dilute solution into the concentrated solution, where both solutions are separated by a semipermeable membrane. 

The osmotic pressure would be zero if pure water were on both sides of the semi-permeable membrane. 

So the correct answer is "0"

Multiple choice physics pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

A sphere floats in water just submerged as shown in the diagram. If atmospheric pressure is neglected

  1. Force exerted by liquid on lower half of sphere is $\dfrac{4\rho\pi\ R^{2}}{3}g$

  2. Force exerted by liquid on lower half of sphere and upper half of sphere is same in magnitude
  3. Ratio of magnitude of forces exerted by liquid on lower and upper half of sphere is $5:1$
  4. Ratio of magnitude of forces exerted by liquid on lower and upper half of sphere is $4:1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a sphere just submerged, the pressure varies with depth. The force on the lower half is greater than the force on the upper half due to the hydrostatic pressure gradient, resulting in a ratio of 5:1.

Multiple choice physics pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

A barometer tube, containing mercury, is lowered in a vessel containing mercury until only $50 cm$ of the tube is above the level of mercury in the vessel. If the atmospheric pressure is $75 cm$ of mercury, what is the pressure at the top of the tube

  1. $33.3 kPa$
  2. $66.7kPa$
  3. $3.33 MPa$
  4. $6.67 MPa$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since the mercury rises only $50cm$ it implies the rest of the excess atmospheric pressure is being countered by the pressure at the top of the tube.
So pressure at top=atmospheric pressure - $50cm$ of Hg=$(75-50)cm=25cm$ of Hg=$1/3\times 100kPa= 33.33kPa$

Multiple choice physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

A narrow uniform glass  tube $80\ cm$ long and open at both ends is half immersed in mercury. Then, the top of the tube is closed and it is taken out of mercury. A column of mercury $22\ cm$ long then remains in the tube. What is the atmospheric pressure?

  1. $60\ cm$ of $Hg$
  2. $70.9\ cm$ of $Hg$
  3. $76\ cm$ of $Hg$
  4. $none$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using Boyle's Law (P1V1 = P2V2) for the trapped air, the atmospheric pressure can be calculated based on the mercury column height and the tube dimensions.

Multiple choice physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

one -meter long tube closed at both the ends is lying horizontally. A mercury column of length 0.1 m is filled in its middle and in rest in two parts air is filled at atmospheric pressure. when the tube is turned to verticle position then displacement of mercury column will be 

  1. 29m

  2. 0.29m

  3. 0.029m

  4. 2.9m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the tube is vertical, the pressure difference between the two air columns balances the weight of the mercury column. Using the ideal gas law and the change in volume, the displacement can be calculated.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a solid is completely immersed in a fluid, the apparent loss of weight of solid is _______ volume of fluid displaced 

  1. more than

  2. less than

  3. equal to

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

From the principle of Archimedes, loss of weight is equal to the weight of the liquid displaced.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a body is fully immersed in a liquid the apparent loss in the weight of body is equal to :

  1. volume of liquid displaced by the body

  2. density of the liquid

  3. weight of liquid displaced by the body

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

According to Archimedes principle, the weight of water displaced is equal to the weight of immersed part.For a solid floating in a liquid, its weight acting vertically down at its centre of gravity is equal to the weight of the liquid displaced by the immersed part of the solid acting vertically up at its centre of buoyancy. In the floating condition, the apparent weight and the apparent density of the solid are zero and the body is said to be weightless.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

State whether the weight of an iron sinker with cork combined in water will be more or less than that of the iron sinker alone in water. 

  1. Less

  2. More

  3. Same

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

The weight of an iron sinker with cork combined in water will be less than that of the iron sinker alone in water.
This is because upthrust on cork due to water (when completely immersed) is greater than its weight.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

An incompressible liquid of density $\rho$ is contained in a vessel of uniform cross-sectional area $A$. If then atmospheric pressure is $p$, then the force acting on a horizontal plane of area a situated at a depth $d$ in liquid is given by

  1. $Ap+apgd$
  2. $\dfrac { p }{ A } +\dfrac { \rho gd }{ a }$
  3. $\dfrac { p+\rho gd }{ a }$
  4. $a\left( \rho\ gd+p \right)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pressure at depth d is P = p + rho*g*d. Force is pressure times area. Thus, F = P * a = (p + rho*g*d) * a = a(p + rho*g*d).

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

A cylindrical container is filled with water upto the brim. If the pressure exerted by the water at the bottom of the container is 1000 Pa the height of the container is ..........cm.(take $g = 10 m s^{-2}$)

  1. 10

  2. 100

  3. 1

  4. 20
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

pressure inside a fluid = $\rho gh$ , in this case $\rho$ = 1000 kg $  m^{3}$

so , 
1000 =  (1000)(10) (h)
hence h = 0.1 m = 10 cm
hence option (A) is correct

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

A beaker is filled with a liquid of density $\rho$ upto a height h. If the beaker is at rest , the mean pressure on the walls is 

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

Pressure varies linearly with depth from 0 at the surface to rho*g*h at the bottom. The mean pressure is the average of these two values: (0 + rho*g*h) / 2 = (rho*g*h) / 2.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

The pressure at the bottom of a water tank is 4P, where P is atmospheric pressure. If water is drawn out till the water level decrease by $\frac{3}{5}$ the, then pressure at the bottom of the tank is 

  1. $\frac{3P}{8}$
  2. $\frac{7P}{6}$
  3. $\frac{11P}{5}$
  4. $\frac{9P}{4}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial pressure at bottom is P_atm + rho*g*H = 4P. Thus, rho*g*H = 3P. If level decreases by 3/5, the new depth is 2/5*H. New pressure = P_atm + rho*g*(2/5*H) = P + 2/5*(3P) = P + 6P/5 = 11P/5.