forces in fluids area the area of a surface is the number of square units that it covers. to find...
TRANSCRIPT
Forces in Fluids
Area The area of a surface is the number of square units that it covers. To find the area of a rectangle, multiply its length by its width. The area of the rectangle below is 2 cm X 3 cm, or 6 cm2.
- Pressure
Forces in Fluids - Pressure
What Is Pressure?
Pressure decreases as the area over which a force is distributed increases.
Forces in Fluids
Pressure = Force Area
UnitsForce Newtons (N)
Area Meters squared (m2)
Pressure N = Pascal (Pa)
m2
Forces in Fluids - Pressure
Fluid Pressure
All of the forces exerted by the individual particles in a fluid combine to make up the pressure exerted by the fluid.
Forces in Fluids - Pressure
Variations in Fluid Pressure
As your elevation increases, atmospheric pressure decreases.
Forces in Fluids - Pressure
Variations in Fluid Pressure
Water pressure increases as depth increases.
Forces in Fluids
Previewing VisualsBefore you read, preview Figure 5. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
Pressure Variations
Q. Why does the pressure change with elevation and depth?
A. Air and water exert pressure, so pressure varies depending on how much air or water is above you.
Q. How much greater is water pressure at a depth of 6,500 m than it is at sea level?
A. It is about 650 times greater.
- Pressure
Forces in Fluids - Floating and Sinking
Buoyancy
The pressure on the bottom of a submerged object is greater than the pressure on the top. The result is a net force in the upward direction.
Forces in Fluids - Floating and Sinking
Buoyancy
The buoyant force acts in the direction opposite to the force of gravity, so it makes an object feel lighter.
Forces in Fluids - Floating and Sinking
Buoyancy
Achimedes’ principle states that the buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces.
Forces in Fluids - Floating and Sinking
Buoyancy
A solid block of steel sinks when placed in water. A steel ship with the same weight floats.
Forces in Fluids - Floating and Sinking
Density
Changes in density cause a submarine to dive, rise, or float.
Forces in Fluids
Relating Cause and EffectAs you read, identify the reasons why an object sinks. Write them down in a graphic organizer like the one below.
Object sinks.
Weight is greater than buoyant force.
Object is denser than fluid.
Object takes on mass and becomes denser than fluid.
Object is compressed and becomes denser than fluid.
- Floating and Sinking
Effect
Causes
Forces in Fluids
PressureP = F N
A m2
Pascal’s Principal
Pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid and to the walls of the container.
Forces in Fluids
Hydraulic Lift
F2, A2
F1, A1
P1 =P2
Therefore:F1 = F2
A1 A2
Forces in Fluids
How Airplanes Wings Work
Forces in Fluids
Density
Click the Video button to watch a movie about density.
- Floating and Sinking
Forces in Fluids
Bernoulli Principle:
States that as the speed of a moving fluid increases, the pressure within the fluid decreases
Forces in Fluids
Bernoulli’s Principle Bernoulli’s Principle is what allows birds is what allows birds and planes to fly.and planes to fly.
The secret behind The secret behind flight is ‘under the flight is ‘under the wings.’wings.’
Forces in Fluids
AIRFOIL
On top: greater air speed and less air pressure
On bottom: less air speed and more air pressure
Forces in Fluids
DRAGDRAG THRUSTTHRUST
LIFTLIFT
GRAVITYGRAVITY
Forces in FluidsSpoiler – airfoil reversed
greater air speedless pressure
less air speedmore pressure
net force: downward
Forces in Fluids
Racecar
Spoiler provides better Traction and avoids lift
greater air speedless pressure
less air speedmore pressure
net force: downward
Forces in Fluids
slow air speed
fast air speed
Forces in Fluids
Curve Ball
Forces in Fluids
Atomizer – As air passes at top of tube, the pressure decreases and fluid is drawn upthe tube.