Bernoulli's Theorem

Air in steady motion posseses 4 types of energy which in total represents the total energy possesed by that particular parcel of air. They are:
- Kinetic energy
- Heat energy
- Pressure energy
- Potential energy

Kinetic energy is formed due to relative movement and is related to potential energy. This is because potential energy, as the name implies, posseses energy that can be exchanged for kinetic energy due to excess height. Heat energy and pressure energy both posses energy due to temperature and static pressure. Bernoulli discovered that the sum of these energies remains constant in a steady and streamline flow. Therefore we can make up the following equation:

Pressure energy + Kinetic energy = Constant

Kinetic energy (½ x mass x velocity squared) can be expressed as ½ x ρ x velocity squared (dynamic pressure), where air density is equivalent to mass for a given volume. In this case the energy equation can be written as:

Static Pressure + Dynamic Pressure = Constant

Combining both the "equation of continuity" with Bernoulli's theorem, it follows that an increase in velocity (thus an increase in dynamic pressure) results in a decrease of static pressure.

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