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All questions of Bernoulli’s Equation for EmSAT Achieve Exam

Water is flowing through a pipe under constant pressure. At some place the pipe becomes narrow. The pressure of water at this place:
  • a)
    remains the same
  • b)
    depends on several factors
  • c)
    decreases
  • d)
    increases
Correct answer is option 'C'. Can you explain this answer?

Suresh Iyer answered
We know that the continuity theorem says that if the cross sectional area of the water flow decreases, the speed must increase to maintain the volume of water flown. And according to Bernoulli's principle if the speed of water flow increases , then the pressure must decrease.

Water is flowing through a horizontal pipe in streamline flow at the narrowest part of the pipe:
  • a)
    Both pressure and the velocity remains constant
  • b)
    velocity is maximum and pressure is minimum
  • c)
    both the pressure and velocity are maximum
  • d)
    both the pressure and velocity are minimum
Correct answer is option 'B'. Can you explain this answer?

Geetika Shah answered
In streamline flow, the product of cross section area and velocity remains constant (equation of continuity). So in the narrowest part of the pipe velocity is maximum. 
And from Bernoulli's theorem, we know that the sum of potential energy, kinetic energy and pressure energy remains constant. Since pipe is horizontal potential energy is equal at all the points. So the narrowest part  of pipe pressure (pressure energy) will be minimum because velocity (kinetic energy) is maximum in the narrowest part.

In which of the following types of flows is the Bernoulli’s theorem strictly applicable:
  • a)
    Streamlined and rotational
  • b)
    Turbulent and rotational
  • c)
    Turbulent and irrotational
  • d)
    Streamlined and irrotational
Correct answer is option 'D'. Can you explain this answer?

Suresh Iyer answered
Bernoulli's principle is applicable on those non-viscous liquids which have laminar flow or streamlined flow.
It means that a liquid in which its particles exert no force on each other, i.e., the speed of all the particles of the liquid is same.
Also, the liquid should travel in the form of streamlines, i.e., the liquid flowing in one pipeline (imaginary pipeline) should not mix in the liquid in another pipeline. This is called streamlined flow.
Also, turbulent flow is the opposite of streamlined flow. So, turbulent liquid will not obey Bernoulli's principle.
But if the liquid is rotated, this streamlined flow will not take place. Thus Bernoulli's principle will not be applicable to this type of liquid.

Bernoulli’s theorem is important in the field of:
  • a)
    Photoelectric effect
  • b)
    flow of liquids
  • c)
    Magnetism
  • d)
    Electrical cells
Correct answer is option 'B'. Can you explain this answer?

Rohan Singh answered
Bernoulli's theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar.

In the houses far away from the municipal water tanks often people find it difficult to get water on the top floor. This happens because
  • a)
    water wets the pipe
  • b)
    the pipes are not of uniform diameter
  • c)
    the viscosity of the water is high
  • d)
    of loss of pressure during the flow of water
Correct answer is option 'D'. Can you explain this answer?

Om Desai answered
Every foot of elevation change causes a 0.433 PSI change in water pressure. If your pipe is going downhill add 0.433 PSI of pressure per vertical foot the pipe goes down. If the pipe is going uphill subtract 0.433 PSI for every vertical foot the pipe goes up.

 Bernoulli’s principle is based on the conservation of:
  • a)
    • Momentum
  • b)
    Energy and momentum both
  • c)
    Mass
  • d)
    Energy
Correct answer is option 'D'. Can you explain this answer?

Rahul Bansal answered
Bernoulli's principle can be derived from the principle of conservation of energy. This states that, in a steady flow, the sum of all forms of energy in a fluid along a streamline is the same at all points on that streamline.

Water is flowing through a pipe under constant pressure. At some place the pipe becomes narrow. The pressure of water at this place:
  • a)
    remains the same
  • b)
    depends on several factors
  • c)
    decreases
  • d)
    increases
Correct answer is option 'C'. Can you explain this answer?

Om Desai answered
Given, That area of cross section at initial point is more than the final point,
From the equation of continuity, we can say that velocity at the final point is more than initial point.
Bernoulli theorem states that
At final point, the velocity is more, so the pressure will be less.
Therefore the pressure decreases

Orifice meter consists of a flat rectangular plate.
  • a)
    True
  • b)
    False
Correct answer is option 'B'. Can you explain this answer?

Sharmila Gupta answered
Introduction:
The orifice meter is a type of flow meter used to measure the flow rate of fluid through a pipe. It consists of a flat rectangular plate with a small hole, known as an orifice, through which the fluid passes. This question is asking whether the given statement about the orifice meter is true or false.

Explanation:
The correct answer is option 'B', which states that the given statement is false. Let's understand why this is the correct answer.

Orifice Plate:
The orifice meter typically consists of a circular orifice plate rather than a flat rectangular plate. The orifice plate is installed perpendicular to the flow direction and creates a pressure difference across itself. This pressure difference is then used to determine the flow rate of the fluid.

Working Principle:
When the fluid passes through the orifice plate, it experiences a reduction in cross-sectional area, leading to an increase in fluid velocity. According to Bernoulli's principle, this increase in velocity corresponds to a decrease in pressure. The pressure difference across the orifice plate is measured using pressure taps located upstream and downstream of the plate.

Calculation of Flow Rate:
The flow rate through the orifice meter can be calculated using various equations, such as the Bernoulli equation, the continuity equation, and the discharge coefficient. These equations take into account the pressure difference, the properties of the fluid, and the dimensions of the orifice plate.

Advantages and Disadvantages:
The orifice meter has several advantages, including simplicity, low cost, and wide applicability. However, it also has limitations, such as pressure loss, sensitivity to changes in fluid properties, and the need for accurate calibration.

Conclusion:
In conclusion, the orifice meter used for measuring fluid flow does not consist of a flat rectangular plate. Instead, it employs a circular orifice plate. Therefore, the given statement is false.

In case of any orifice, velocity always remains constant and hence discharge can be calculated.
  • a)
    True
  • b)
    False
Correct answer is option 'B'. Can you explain this answer?

False

Explanation:
In case of any orifice, the velocity does not always remain constant. The velocity of fluid flowing through an orifice depends on various factors such as the size of the orifice, the pressure difference across the orifice, and the properties of the fluid. Therefore, the discharge cannot be calculated solely based on the assumption that the velocity remains constant.

Factors affecting the velocity and discharge through an orifice:

1. Size of the orifice: The size of the orifice affects the velocity and discharge of the fluid. A smaller orifice will result in a higher velocity and discharge, while a larger orifice will result in a lower velocity and discharge.

2. Pressure difference across the orifice: The pressure difference across the orifice also affects the velocity and discharge. A higher pressure difference will result in a higher velocity and discharge, while a lower pressure difference will result in a lower velocity and discharge.

3. Properties of the fluid: The properties of the fluid, such as its density and viscosity, also play a role in determining the velocity and discharge. A more viscous fluid will have a lower velocity and discharge compared to a less viscous fluid.

Calculation of the discharge through an orifice:

The discharge through an orifice can be calculated using the following equation:

Q = Cd * A * √(2gh)

Where:
Q = Discharge
Cd = Coefficient of discharge
A = Area of the orifice
g = Acceleration due to gravity
h = Head difference across the orifice

The coefficient of discharge takes into account the various factors that affect the velocity and discharge, such as the shape of the orifice, the roughness of the edges, and the contraction and expansion of the flow. Therefore, it is necessary to consider these factors and use the appropriate value of the coefficient of discharge in the calculation.

Conclusion:

In conclusion, the velocity does not always remain constant in case of any orifice. The velocity and discharge through an orifice depend on various factors such as the size of the orifice, the pressure difference across the orifice, and the properties of the fluid. Therefore, it is important to consider these factors and use the appropriate equations, such as the discharge equation mentioned above, to calculate the discharge accurately.

Water is flowing through a horizontal tube. The pressure of the liquid in the portion where velocity is 2 m/s is 2 m of Hg. What will be the pressure in the portion where velocity is 4 m/s?
  • a)
    430 x 10³ Pa
  • b)
    4.3 x 10³ Pa
  • c)
    1.31 x 105 Pa
  • d)
    0.43 x 10³ Pa
Correct answer is option 'C'. Can you explain this answer?

Sparsh Datta answered
We know that Pv remains constant for any fluid and for non compressible fluids like water we get that Pv is always constant.
Also as 76cm of Hg = 105 Pa  
We get 2m Hg = 200/76 x 105 Pa
Thus from conservation of Pv, we get that
2 x  200/76 x 105  = 4 x P
Thus we get P = 100/76 x 105
Thus we get P = 1.31 x 105

Bernoulli’s theorem includes as a special case of:
  • a)
    Torricelli’s law
  • b)
    Hooke’s law
  • c)
    Archimedes’ principle
  • d)
    Pascal’s law
Correct answer is option 'A'. Can you explain this answer?

Rohan Singh answered
Bernoulli’s Theorem
Bernoulli’s theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar. First derived (1738) by the Swiss mathematician Daniel Bernoulli, the theorem states, in effect, that the total mechanical energy of the flowing fluid, comprising the energy associated with fluid pressure, the gravitational potential energy of elevation, and the kinetic energy of fluid motion, remains constant. Bernoulli’s theorem is the principle of energy conservation for ideal fluids in steady, or streamline, flow and is the basis for many engineering applications.

The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.
  • a)
    True
  • b)
    False
Correct answer is option 'B'. Can you explain this answer?

Aarav Chauhan answered
Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.

To which type of fluid is the Bernoulli’s theorem applicable:
  • a)
    Incompressible and anisotropic
  • b)
    Incompressible and viscous
  • c)
    Compressible and anisotropic
  • d)
    Incompressible, isotropic and non viscous
Correct answer is option 'D'. Can you explain this answer?

Akshay Shah answered
Bernoulli's theorem. Bernoulli's theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar.

Bernoulli’s principle is based on the conservation of:
  • a)
    Momentum
  • b)
    Energy and momentum both
  • c)
    Mass
  • d)
    Energy
Correct answer is option 'D'. Can you explain this answer?

Rounak Goyal answered
The Bernoulli equation is an important expression relating pressure, height and velocity of a fluid at one point along its flow. Because the Bernoulli equation is equal to a constant at all points along a streamline, we can equate two points on a streamline.

Which is the cheapest device for measuring flow / discharge rate.
  • a)
    Venturimeter
  • b)
    Pitot tube
  • c)
    Orificemeter
  • d)
    None of the mentioned
Correct answer is option 'C'. Can you explain this answer?

Cheapest device for measuring flow/discharge rate

Orificemeter is the cheapest device for measuring flow/discharge rate among the given options.

Explanation

Orificemeter is a device used for measuring the flow of fluids. It consists of a flat plate with a hole in the center. When the fluid flows through the hole, its velocity increases and its pressure decreases. By measuring the pressure difference between the upstream and downstream sides of the plate, the flow rate can be calculated.

The cost of orificemeter is relatively low compared to other flow measuring devices like venturimeter and pitot tube. This is because orificemeter is a simple device with no moving parts and can be easily installed.

On the other hand, venturimeter and pitot tube are more complex devices with multiple components and require precise installation to accurately measure the flow. Therefore, these devices are more expensive than orificemeter.

Conclusion

In conclusion, orificemeter is the cheapest device for measuring flow/discharge rate among the given options. It is a simple and reliable device that can be easily installed and maintained.

Bernoulli’s theorem is important in the field of:
  • a)
    Photoelectric effect
  • b)
    Flow of liquids
  • c)
    Magnetism​
  • d)
    Electrical cells
Correct answer is option 'B'. Can you explain this answer?

Rounak Goyal answered
The Bernoulli equation is an important expression relating pressure, height and velocity of a fluid at one point along its flow. Because the Bernoulli equation is equal to a constant at all points along a streamline, we can equate two points on a streamline.

A nanometre is connected to a section which is at a distance of about 4 to 6 times the pipe diameter upstream from orifice plate.
  • a)
    True
  • b)
    False
Correct answer is option 'B'. Can you explain this answer?

Explanation: A manometre is connected to a section which is at a distance of about 1.5 to 2.0 times the pipe diameter upstream from orifice plate.

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