LECTURE 10 (Hydrostatics) Flashcards
What are the properties of Fluid?
- Cannot maintain equilibrium condition under various influences
- Deforms/begins movement due to influence
- Fluid compression is very low
What is Pressure?
The force per unit area applied in a direction perpendicular to the surface of an object
What is Liquid pressure?
The force per unit area of hard substance from liquid layer or liquid itself
P = F/S
P - Fluid pressure
F - Pressure force
S - Surface area
What is the equation for Pressure force?
F = PS
F - Pressure force
P - Fluid pressure
S - Surface area
What is pressure measured in?
Pascal (Pa)
Explanation: Pressure equals 1 Pascal, if per 1 m2 area surface is influenced by 1 Newton force
What does Pascal’s law state?
Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid
What is Fluid hydrostatic pressure?
The pressure of non-moving (static) fluid determined by exertion of gravity forces on fluid (fluid mass)
Hydrostatics is based on two principles:
- Pascal’s law
- The pressure ratio remains the same in all points of horizontal plane
What is the difference between water horizontally and vertically?
Horizontally = water pressure is the same (P1 = P2 = P3)
Vertically = water pressure increased with depth (pgh = density x gravity x height)
What is the U-pipe principle?
Pressure increase in one bend of U-pipe causes pressure increase in another bend with the same value
What does Atmospheric pressure equal?
The weight of mercury
What is the standard atmosphere?
A unit of pressure defined as 101325 Pa or 760 mmHg
What is a Manometer?
- Comprised of a bulb containing a gas and a U-shaped tube partially filled with mercury
- Measure static pressure
- If both ends of U-pipe fluid level equal -> object’s pressure is equal to atmospheric pressure
- If open bend of manometer fluid level raises -> object’s pressure is higher than atmospheric pressure
What is the difference between fluid levels in manometer bends determined by?
Δp value
[Δp = h]
Explanation: Δp value shows how object pressure differs from atmospheric pressure
What is Decompression sickness?
Also called “the bends”, Caisson sickness or “diver’s disease” is a life threatening condition caused by a buildup of nitrogen bubbles in the bloodstream and body tissues
CAUSE:
As a diver descends, pressure increases -> Nitrogen is absorbed into the body tissues -> Diver must ascend SLOWLY to allow nitrogen to escape out of the body -> If diver ascends too fast, nitrogen becomes bubbles in the tissue + bloodstream
SYMPTOMS:
- Unusual fatigue
- Skin itch
- Pain in joints and/or muscles of arms, legs or torso
- Dizziness, vertigo, ringing in ears
- Numbness, tingling and paralysis
- Shortness of breath
TREATMENT:
Recompression in a HIGH-PRESSURE HYPERBARIC CHAMBER in which the patient is put back under pressure and receives 100% oxygen -> reverses pressure changes that allows gas bubbles to form + drives back into liquid form that can be gradually cleared
Pressure in a mixture of gases follows which principles?
- Each gas exerts the same pressure that it would if it alone occupied the container
- Pressure each gas exerts is called its “Partial pressure” and the total pressure is “the sum of the partial pressure of the constituent gases”
- Ratio of the partial pressure of any component to the total pressure equals the ratio of its partial volume to the total volume
- Gasses dissolved in water also exert pressure (since move randomly + have kinetic energy)
