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 intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

A capillary tube of radius $0.25\ mm$ is submerged vertically in water so that $25\ mm$ of its length outside water. The radius of curvature of the meniscus will be $(T = 7.5\times 10^{-3} N/m)$.

  1. $0.2\ mm$
  2. $0.4\ mm$
  3. $0.6\ mm$
  4. $0.8\ mm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$h= \dfrac{2T}{dgx}$

$h= \dfrac{2\times 7.5 \times {10}^-3} {1000 \times 10 \times d}$
$h=25mm$
$d= 0.6 mm$

Multiple choice commercial applications receding water table water and ocean conservation water resources and conservation water conservation and irrigation

What is density of water?

  1. 987kg/m3

  2. 997kg/m3

  3. 897kg/m3

  4. 797kg/m3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The density of pure water at standard atmospheric pressure and 4 degrees Celsius is approximately 1000 kg/m3. Among the provided choices, 997 kg/m3 is the closest scientific approximation for water at room temperature.

Multiple choice evs nature of things properties of materials grouping and classification of objects sorting materials into groups

The density of alcohol is 800 $ \displaystyle Kg/m^{3} $. Its relative density is:

  1. 8

  2. 0.8

  3. 0.08

  4. 800
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Relative density is the ratio of the density of the substance to the density of water.

We know that, density of water is $1 gm/cm^3   = 10^3 kg/m^3$

So, relative density of alcohol = $\dfrac{800}{1000}$ = $0.8$

Hence, option B is correct.
Multiple choice evs nature of things properties of materials grouping and classification of objects sorting materials into groups

A block of iron (density 9.8 $ \displaystyle g/cm^{3}) $ if added in mercury (density 13.6 $ \displaystyle g/cm^{3} $ ) will:

  1. sink

  2. float

  3. neither float nor sink i.e. remain suspended in mercury

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

The average density of the object should be less than the density of the fluid in which the object has to float.


The density of object (iron) is less than the fluid (mercury).

Therefore, it will float.


Hence, option B is correct.

Multiple choice chemistry changes around us can all changes be reversed? substances and objects classification of changes

The density of a certain solid object is greater than the density of the liquid. If  it is placed in water, the object will :

  1. sink

  2. expand

  3. float

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

When solid is placed in water, the density of solid decides if it will float or sink in water. 


If the density of solid is higher than liquid water it sinks because according to Archimedes principle, the buoyancy force is not enough to hold it in place.

i.e. if solid density > liquid - sinks

     if solid density < liquid - floats


Hence the correct option is A.

Multiple choice physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

Which of the following properties represent a hydrometer?
a. It helps to evaluate the relative density and purity of liquids.
b. The length of the hydrometer immersed in any liquid is directly proportional to the density of the liquid.
c. The relative density graduations on a hydrometer increase in the upward direction.
d. Water is regarded as a standard to find the relative density of any liquid using a hydrometer.

  1. a, b and c

  2. a and d

  3. a, b and d

  4. b and d
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hydrometer is a device used for directly measuring the relative density of a liquid with respect to water and hence helps to test the liquids purity. A hydrometer tube submerges less in a liquid of higher relative density and more in a liquid of lower relative density with regard to water. Thus the graduations on the hydrometer test tube show increase in relative density in the downward direction as it sinks less in a liquid of higher relative density.

Multiple choice physics fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

Hydraulic press works on the principle of Pascal's principle

  1. True

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

Pascal law states that any increment in pressure applied to the enclosed fluid is transmitted undiminished at each pt of the fluid and the walls of the container.

and  hydraulic press works on the principle of pascal law 
so option (A) is correct.

Multiple choice physics fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

Lifting automobiles in service stations is based on the principle of ________.

  1. Apparent pressure

  2. Hydraulic pressure

  3. Atmospheric pressure

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

Lifting automobiles in service stations is based on the principle of Hydraulic pressure .

hydraulic press is based on the pascal law .
so option (B) is correct

Multiple choice physics pressure in fluids and atmospheric pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

Two identical holes of each of cross sectional area $A$ are opened on the opposite sides of a wide vertical vessel filled with water.The difference in vertical height of the two holes is $h$. The resultant force of reaction of water flowing out of vessel is-

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

The velocity of efflux is v = sqrt(2gh). The force of reaction is F = dm/dt * v = (rho * A * v) * v = rho * A * v^2. Since there are two holes, the total force is 2 * rho * A * (2gh) = 4 * rho * A * g * h. Given the specific geometry, the standard result for this problem is 2 * rho * A * g * h.

Multiple choice lorentz transformation and muon experiment option a: relativity physics

An air-bubble rises from the bottom of a long and narrow glass-tube full of glycerine. What happens to the speed of the air-bubble till it comes to the top?

  1. It goes on increasing

  2. It goes on decreasing

  3. It first increases, then moves up with constant velocity

  4. The speed remains the same throughout
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As an air bubble rises in a viscous liquid like glycerine, it accelerates initially due to buoyancy, but then reaches a terminal velocity where the buoyant force, gravity, and viscous drag balance out.

Multiple choice examples of circular motion uniform circular motion circular motion and gravitation physics

A small bucket containing water is rotated in a vertical circle of radius $R$ by means of a rope. $v$ is velocity of bucket at highest point. Then water does not fall down if:

  1. $v \leq \sqrt{gR}$
  2. $v \leq \sqrt{\frac{gR}{2}}$
  3. $v \geq \sqrt{gR}$
  4. $v \geq \sqrt{\frac{gR}{2}}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At highest point the centripetal acceleration should be greater than g.
$\therefore \dfrac{v^{2}}{R}\geq g$


or, $v\geq \sqrt{Rg}$

Multiple choice examples of circular motion uniform circular motion circular motion and gravitation physics

A bucket is whirled in a vertical circle with a string attached to it. The water in the bucket does not fall down even when the bucket is inverted at the top of its path. We can say that in this position.

  1. $mg=\displaystyle\frac{mv^2}{r}$
  2. mg is greater than $\displaystyle\frac{mv^2}{r}$
  3. mg is not greater than $\displaystyle\frac{mv^2}{r}$
  4. mg is not less than $\displaystyle\frac{mv^2}{r}$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

When the bucket is at the top of its path, the forces acting on the water are gravity and centripetal force. Since, the water does not fall down. Therefore, centripetal force is greater than the force of gravity.

Therefore, $\cfrac{mV^2}{R}\ge mg$