HovercraftHovercraft

By: Devin Zenner By: Devin Zenner

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Grace OverendGrace Overend

Picture of our Hovercraft!Picture of our Hovercraft!

Actual PlansActual Plans

PressurePressure PressurePressure P=F/AP=F/A Pressure under hovercraft has to be more than Pressure under hovercraft has to be more than

14.7 psi.14.7 psi. PSIPSI

Pounds per square inch of pressurePounds per square inch of pressure ““normal” psi is 14.7, what we’re used to everydaynormal” psi is 14.7, what we’re used to everydayAs you increase by 10,000 ft. you subtract 4 psi from As you increase by 10,000 ft. you subtract 4 psi from

normal…pressure decreases by altitude.normal…pressure decreases by altitude.Estimate the amount of psi that we will needEstimate the amount of psi that we will need

Take weight that we want to lift divided by the surface Take weight that we want to lift divided by the surface area (of hovercraft).area (of hovercraft).

Bernoulli’s PrincipleBernoulli’s Principle

P+1/2P2+Pgh=C P+1/2P2+Pgh=C As the Velocity of a fluid increases the As the Velocity of a fluid increases the

Pressure exerted by the fluid decreases. Pressure exerted by the fluid decreases. Applies to leafblower and holes in plastic…Applies to leafblower and holes in plastic… http://library.thinkquest.org/27948/bernoulli.htmlhttp://library.thinkquest.org/27948/bernoulli.html

Fluid MechanicsFluid Mechanics

Examples in everyday lifeExamples in everyday lifeAirplaneAirplane

WingsWingsLift/takeoffLift/takeoffLandingsLandings

Army HovercraftsArmy HovercraftsHUGEHUGEHolds 12 HummersHolds 12 HummersWater AND LandWater AND Land

Fluid Mechanics/LiftFluid Mechanics/Lift

LiftLiftMolecules provide the necessary lift.Molecules provide the necessary lift.The more molecules that are present the more The more molecules that are present the more

pressure is built up providing more lift.pressure is built up providing more lift.

Pascal’s PrinciplePascal’s Principle

Pascal’s PrinciplePascal’s PrincipleFluid (air) in a closed container is transmitted Fluid (air) in a closed container is transmitted

equally to every point of the fluid and to the walls equally to every point of the fluid and to the walls of the container.of the container.

Plastic skirt that contains the air provides the Plastic skirt that contains the air provides the necessary lift for the hovercraft.necessary lift for the hovercraft.

Air is equally pushed out of all the holes in the Air is equally pushed out of all the holes in the bottom bottom

Lifts the hovercraft off of the ground.Lifts the hovercraft off of the ground.

Pascal’s Principle ContinuedPascal’s Principle Continued

Necessary for the pressure to be equal throughout Necessary for the pressure to be equal throughout the skirtthe skirt

Prevent uneven lift.Prevent uneven lift.

Pressure is equal to the initial force divided by the Pressure is equal to the initial force divided by the initial area initial area

Also equal to the final force divided by the final area.Also equal to the final force divided by the final area.

P =F1/A1=F2/A2P =F1/A1=F2/A2

Example of Pascal’s PrincipleExample of Pascal’s PrincipleThe small piston of a hydraulic lift has an area of The small piston of a hydraulic lift has an area of

0.20m2. A car weighing 1.20x104N sits on a rack 0.20m2. A car weighing 1.20x104N sits on a rack mounted on the large piston. The large piston has an mounted on the large piston. The large piston has an area of 0.90m2. How large a force must be applied to area of 0.90m2. How large a force must be applied to the small piston to support the car?the small piston to support the car?

Given:Given: A1=0.20m2 A1=0.20m2 A2=0.90m2A2=0.90m2 F2=1.20x104 NF2=1.20x104 N

Unknown:Unknown: F1=?F1=?

Use the equation for pressure and apply Pascal’s Use the equation for pressure and apply Pascal’s principle.principle.

Pascal’s AnswerPascal’s Answer

F1=(A1/A2)F2F1=(A1/A2)F2=(0.20m2/0.90m2)(1.20x104 N)=(0.20m2/0.90m2)(1.20x104 N)

F1=2.7x103 NF1=2.7x103 N

Pictures! Weeeeee!Pictures! Weeeeee!

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