# Manometer Force analysis

In summary, the conversation discusses the forces acting on a manometer in two different cases. In case 1, the atmospheric force exerts a downward force on the fluid, causing the fluid to exert an equal but upward force on the atmosphere. In case 2, if the left side of the manometer is connected to a gas source with higher kinetic energy, the gas molecules will exert a higher pressure and potentially cause the liquid to move or form bubbles. The conversation also suggests using a homemade manometer to observe these effects and recommends learning about the basics of pressure in gases and liquids.

Thread moved from the technical forums to the schoolwork forums
Note: I am self-studying Material and Energy balance courses and I haven't done fluid mechanics yet.

Case 1) Consider the manometer in the figure below. Levels on both sides of the manometer which are open to the atmosphere are equal.
If we analyse the forces acting on the left side of the manometer. We have the atmospheric force exerting a downward force on the fluid and since the fluid is not undergoing acceleration it is either moving at a non zero speed or is stationary. Therefore the fluid must be exerting an equal but upward force on the atmosphere.

Case 2) If we hook up the left side of the manometer to a gas source containing higher kinetic energy molecules than the air molecules on the right side exposed to the atmosphere then those gas molecules are exerting a higher pressure. What would happen in this case?
Will the gas molecules push the liquid, bounce, pass through the liquid as bubbles?

I wrote case (1) mainly to link the upward force the fluid exerts and what is it a function of?

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Note: I am self-studying Material and Energy balance courses and I haven't done fluid mechanics yet.

Case 1) Consider the manometer in the figure below. Levels on both sides of the manometer which are open to the atmosphere are equal.
If we analyse the forces acting on the left side of the manometer. We have the atmospheric force exerting a downward force on the fluid and since the fluid is not undergoing acceleration it is either moving at a non zero speed or is stationary. Therefore the fluid must be exerting an equal but upward force on the atmosphere.
By Newton's law of action-reaction, the fluid exerts and equal but upward force on the atmosphere no matter what else is going on.

Case 1) Consider the manometer in the figure below. Levels on both sides of the manometer which are open to the atmosphere are equal.
If we analyse the forces acting on the left side of the manometer. We have the atmospheric force exerting a downward force on the fluid and since the fluid is not undergoing acceleration it is either moving at a non zero speed or is stationary. Therefore the fluid must be exerting an equal but upward force on the atmosphere.

Case 2) If we hook up the left side of the manometer to a gas source containing higher kinetic energy molecules than the air molecules on the right side exposed to the atmosphere then those gas molecules are exerting a higher pressure. What would happen in this case?
Will the gas molecules push the liquid, bounce, pass through the liquid as bubbles?

I wrote case (1) mainly to link the upward force the fluid exerts and what is it a function of?

In case 1, the magnitude of the force depends on the value of atmospheric pressure and the area of the liquid’s surface. The value of the atmospheric pressure depends on the average speed and mass of the air molecules and their number-density (how many molecules there are per cubic metre).

For case 2, I recommend you get a length of (clean!) clear plastic tube with some water. You can hold the tube in a U-shape and you have made your own manometer!

Increase the pressure on one side by gently and briefly blowing into one end. Then quickly slide slide your finger over the end in your mouth (yes it can be done!) to trap the extra gas. You will see what happens.

Similarly, you can reduce the pressure on one side by briefly and gently sucking on one end. Avoid sucking too hard and choking!

It sounds like you may have to take a step back and first learn about the basics about pressure in gases and liquids.

By the way, liquids and gases are often both referred to as ‘fluids’. So here it is best to say that the atmosphere ex erts a force on the liquid (and vice versa).

## 1. What is a manometer force analysis?

A manometer force analysis is a method used to measure the pressure or force exerted by a fluid in a closed system. This is typically done by comparing the fluid's pressure to a reference pressure, such as atmospheric pressure.

## 2. How does a manometer work?

A manometer works by using a column of liquid, typically mercury or water, to measure the pressure of a gas or liquid in a closed system. The height of the liquid column is directly proportional to the pressure being measured.

## 3. What are the different types of manometers?

There are several types of manometers, including U-tube, inclined, and well-type manometers. U-tube manometers have a U-shaped tube filled with liquid, while inclined manometers use a slanted tube. Well-type manometers have a reservoir of liquid connected to a tube.

## 4. What are some common uses of manometer force analysis?

Manometer force analysis is commonly used in industries such as HVAC, plumbing, and automotive to measure pressure in pipes, tanks, and other closed systems. It is also used in laboratory settings for experiments and research.

## 5. What are some factors that can affect the accuracy of a manometer reading?

The accuracy of a manometer reading can be affected by factors such as the type and density of the liquid used, the temperature of the liquid and surrounding environment, and the level of precision in the measurement equipment. Additionally, any air bubbles or leaks in the system can also impact the accuracy of the reading.

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