Physics

Fluid Mechanics and Hydraulics

376 Questions

Fluid mechanics and hydraulics questions address the principles of fluid flow, pipe resistance, and open channel dynamics. The topics include Bernoulli equation, Navier-Stokes equation, and hydrograph calculations. These concepts are crucial for civil and mechanical engineering competitive examinations.

Fluid flow equationsOpen channel flowPipe frictionHydraulic jumpHydrograph analysis

Fluid Mechanics and Hydraulics Questions

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

A ${ 16cm }^{ 3 }$ volume of water flows per second through a capillary tube of radius r cm and of length 1 cm, when connected to a pressure head of h cm of water. If a tube of the same length and radius r/2 is connected to the same pressure head, find the mass of water flowing per minute through the tube 

  1. 80 gram/min

  2. 70 gram/min

  3. 60 gram/min

  4. 50 gram/min
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Poiseuille's law, flow rate Q is proportional to r^4. If the radius is halved (r/2), the flow rate becomes (1/2)^4 = 1/16 of the original. Original flow = 16 cm^3/s. New flow = 1 cm^3/s. Mass per minute = 1 cm^3/s * 60 s = 60 grams/min.

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

If it takes $5$ minutes to fill a 15 litre bucket  from a water tap of diameter $\frac{2}{\sqrt{\pi}}$ cm then the Reynolds number for the flow is (density of water = $10^3 kg/m^3$ and viscosity of water = $10^{-3}$Pa.s) close to

  1. $11,000$
  2. $550$
  3. $1100$
  4. $5500$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Flow rate = 15L/5min = 3L/min = 0.00005 m³/s. Radius = (2/√π)/100 = 0.0113 m. Velocity = Q/A = 0.00005/(π×0.0113²) ≈ 0.125 m/s. Reynolds = ρvd/η = (10³)(0.125)(0.0226)/(10⁻³) ≈ 2825. Closest to 5500 among options, indicating turbulent flow.

Multiple choice physics turning effects of forces centre of gravity forces - vectors and moments acceleration due to gravity

For a ball falling in a iiquid with constant velocity, ratio of resistance force due to the liquid to that due to gravity is 

  1. $\frac{{2{a^2}\rho g}}{{9xv}}$
  2. $\dfrac { 2 a ^ { 2 } \rho g } { 9 \eta ^ { 2 } }$
  3. $\dfrac { 2 a ^ { 2 } ( \rho - \sigma ) g } { 9 \eta }$

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

Force due to liquid (stokes law):

$f = 6\pi xrv$
Force due to gravity:
$\begin{array}{l} f=mg \ =\rho .\dfrac { { 4\pi { r^{ 3 } } } }{ 3 } .g \end{array}$
Ratio =
$\ \begin{array}{l} \dfrac { { 4\rho .\pi { r^{ 2 } }.g } }{ { 3.6\pi xr.v } }  \ =\dfrac { { 2{ a^{ 2 } }\rho g } }{ { 9xv } }  \end{array}$
$\therefore \,\,\,\,\,\dfrac{{2{a^2}\rho g}}{{9xv}}$
so,
Option $A$ is correct answer.

Multiple choice social science universe and space the big bang and the early development of the universe origin of universe evolution of the universe

When the flow parameters of any given instant remain same at every point, then flow is said to be

  1. laminar

  2. steady state

  3. turbulent

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

When the flow parameters (like pressure, velocity etc) doesn't change w.r.t time i.e remains constant through out the time period, then this state is called as STEADY STATE.

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

Water is floating smoothly through a closed-pipe system. At one point $A$, the speed of the water is $3.0\ m$ while at another point $B$, $1.0\ m$ higher, the speed is $4.0\ m/s$. The pressure at $A$ is $20\ kPa$ when the flowing $18\ kPa$ when the water flow stop. Then

  1. the pressure at $B$ when water is flowing is $6.5\ kPa$
  2. the pressure at $B$ when water is flowing is $8.0\ kPa$
  3. the pressure at $B$ when water is flowing is $10\ kPa$

  4. None of these
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

Water enters a house through a pipe with an inside diameter of $2 \,cm$ at an absolute pressure of $4 \times 10^5 \,Pa$. A pipe of diameter $1 \,cm$ leads to the second floor room $5 \,m$ above the entry point. When the flow speed at the inlet is $1.5 \,m/s$. Which of the following statements are correct.

  1. Flow speed on the second floor room is $6 \,m/s$
  2. Volume flow rate in the second floor room is nearly $0.47 \,L/s$
  3. Water pressure in the second floor room is approximately $3.33$ atmosphere
  4. Water pressure in the second floor room is $3.50$ atmosphere
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$4 \times 10^5 + \dfrac{1}{2} \times 1000 \times (1.5)^2 = P _2 + \dfrac{1}{2} \times 1000 \times (6)^2 + 1000 \times 10 \times 5$

$10^3 \left(400 + \dfrac{g}{\theta} \right) = P _2 + 10^3 (10 + 50)$

$P _2 = 10^3 \left(\dfrac{320 \,g}{\theta} - 6\theta \right)$

$= 10^3 \left(\dfrac{320 \,g - 544}{\theta}\right)$

= $10^3 \dfrac{2665}{\theta}$

$= 10^3 \times 333$
$= 3.33 \,atm$

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

A jet of water with cross section of $6{ cm }^{ 2 }$ strikes a wall at an angle of ${ 60 }^{ \circ  }$ to the normal and rebounds elastically from the wall without losing energy. If the velocity of the water in the jet is $12 m/s$, the force acting on the wall is

  1. $0.864N$
  2. $86.4N$
  3. $72N$
  4. $7.2N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
F = $\dfrac{dP}{dt}$
   = $\dfrac{2 dm V\cos 60^o}{dt}$
   = $\dfrac{2 (\rho A dx) V\cos 60^o}{dt}$
   = $2 \rho A {V}^2\cos 60^o$
   = ${10}^3\times 6\times {10}^{-4} \times{12}^2$
   =$86.4N$
Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

A wide vessel with a small hole in the bottom is filled with water and kerosene. Neglecting the viscosity, find the velocity of the water flow, if the thickness of the water layer is equal to $\mathrm { h } _ { 1 } = 30 \mathrm { cm }$ and that of the kerosene layer to $h _ { 2 } = 20 \mathrm { cm }$.Density of kerosene $= 600 \operatorname { kg } / m ^ { 3 }$

  1. $5.74 \mathrm { ms } ^ { - 1 }$
  2. $1.91 \mathrm { ms } ^ { - 1 }$
  3. $2.87 \mathrm { ms } ^ { - 1 }$
  4. $3.82 \mathrm { ms } ^ { - 1 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using Bernoulli's principle at the hole: P_atm + rho_k*g*h2 + rho_w*g*h1 = P_atm + 0.5*rho_w*v^2. v = sqrt(2*(rho_k*g*h2 + rho_w*g*h1)/rho_w) = sqrt(2*(600*10*0.2 + 1000*10*0.3)/1000) = sqrt(2*(1200+3000)/1000) = sqrt(8.4) = 2.89 m/s.

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

Water flows into a large tank with flat bottom at the rate of $  10-4 \mathrm{m}^{3} \mathrm{s}-1  $ . Water is also leaking out
of a hole of area 1 $  \mathrm{cm}^{2}  $ at its bottom. If the height of the water in the tank remains steady, then this height is:

  1. 4 cm

  2. 2.9 cm

  3. 1.7 cm

  4. 5.1 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

How much work is done by an agent fcn forcing 3$\mathrm { m } ^ { 3 }$ of water through a pipe of radius 2$\mathrm { cm }$ , It the difference in pressure at the two ends of the pipe is $10 ^ { 4 } \mathrm { N } \mathrm { m } ^ { 2 } \mathrm { ? }$

  1. $3 \times 10 ^ { 6 } J$
  2. $2 \times 10 ^ { 6 } J$
  3. $4 \times 10 ^ { 5 } J$
  4. $1 \times 10 ^ { 5 } 3$
Reveal answer Fill a bubble to check yourself
A Correct answer