How can a non-flowing fluid have kinetic energy?

In summary, the conversation discussed the energy of non-flowing and flowing fluids. Non-flowing fluids have internal energy, potential energy, and kinetic energy, while flowing fluids have the additional energy of flow energy Pv. There was also a discussion about the difference between internal kinetic energy and regular kinetic energy, as well as the concept of internal energy being a combination of kinetic and potential energy. The conversation also touched on the Bernoulli equation and the inclusion of gravitational potential energy in its terms.
  • #1
eurekameh
210
0
So a non-flowing fluid has energy that consists of internal energy, potential energy, and kinetic energy. If it is "non-flowing," how is this possible?

A flowing fluid has energy that consists of internal energy, potential energy, kinetic energy, and flow energy Pv. My other question is, shouldn't the flow energy be a part of its kinetic energy as well? Why are they different?
 
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  • #2
Is this a homework question?
 
  • #3
Note that in this case, potential energy is gravitational potential energy.

Bernoulli equation with gravitational term, for an ideal fluid with no external forces other than gravity:

pressure + 1/2 ρ v2 + ρ g h = total_energy / unit_volume

If you multiply this by some amount of volume you get energies:

(pressure x volume) + 1/2 m v2 + m g h = total_energy

pressure_energy + kinetic_energy + gravitational_potential_energy = total_energy

I'm not sure where you got the additional term from.
 
  • #4
Make sure you understand that Internal Energy is not some kind of energy; instead it is a concept that includes kinetic and potential energy internal to the body, substance.

Also, make sure you understand the difference between Internal Kinetic Energy and Kinetic Energy in its more common sense.

Internal kinetic energy refers to the motion of the particles in the object, substance.

Regular kinetic energy, the more common concept as understood by most everybody, refers to the kinetic energy of the body as a whole due to its motion, translation.
 
  • #5
The molecules of the fluid are moving, but the fluid doesn't necessarily have to flow.
 
  • #6
Put the liquid in a sealed container wait for it to stop moving from your lifting it and drop it from a height.
 
  • #7
rcgldr said:
Note that in this case, potential energy is gravitational potential energy.

Bernoulli equation with gravitational term, for an ideal fluid with no external forces other than gravity:

pressure + 1/2 ρ v2 + ρ g h = total_energy / unit_volume

If you multiply this by some amount of volume you get energies:

(pressure x volume) + 1/2 m v2 + m g h = total_energy

pressure_energy + kinetic_energy + gravitational_potential_energy = total_energy

I'm not sure where you got the additional term from.

You mean the internal energy term? Here's the equation from my textbook: http://imageshack.us/photo/my-images/850/unledkzh.png/
I can kinda see where everyone's coming from with the internal kinetic energy. But I would guess that would be a part of its total internal energy, which is already a part of the equation.
 

1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is a form of energy that is associated with the movement of an object.

2. How can a non-flowing fluid have kinetic energy?

Even though a non-flowing fluid may not have visible motion, its molecules are constantly in motion due to their thermal energy. This molecular motion gives the fluid kinetic energy.

3. Can a non-flowing fluid have the same amount of kinetic energy as a flowing fluid?

No, a non-flowing fluid typically has less kinetic energy than a flowing fluid because the molecules in a flowing fluid have more organized and directed motion compared to the random motion of molecules in a non-flowing fluid.

4. What factors affect the amount of kinetic energy in a non-flowing fluid?

The amount of kinetic energy in a non-flowing fluid is affected by its temperature, pressure, and the type of fluid. Higher temperatures and pressures generally result in higher kinetic energy, and different fluids have different molecular structures and therefore different amounts of kinetic energy.

5. How is the kinetic energy of a non-flowing fluid measured?

The kinetic energy of a non-flowing fluid can be measured by calculating the average kinetic energy of its molecules using the formula KE = 1/2 mv^2, where m is the mass of the molecule and v is its velocity. However, in practical applications, the total kinetic energy of a non-flowing fluid is usually measured indirectly by measuring other properties, such as temperature and pressure.

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