Unit 2: MatterChapter 3: States of Matter
Section 3: Fluids
Bell RingerCheck your file!!Have you turned in your Science in the News
assignment??Test on Chapter 3 WEDNESDAYUnit 2 Test FRIDAYGet out your notes and get ready
PressurePressure – the amount of force exerted per unit area of a surface
Fluids exert pressure evenly in all directions
P=force/areaMeasured in pascals (Pa)
Buoyant forceBuoyant force – the upward force that keeps an object immersed in or floating on a fluidResults from pressure increasing with depth
Object continues to sink until the forces pushing it up and greater than those pulling it down
Buoyant ForceArchimedes Principle – the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces
if the weight of the water displaced is equal to the buoyant force, the object will float
Sink or float also based on density
Pascal’s PrinciplePascal’s Principle – a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid
P1 = P2
F1/A1 = F2/A2.
Pascal’s Principle A hydraulic lift uses Pascal’s principle to lift a 19,000 N car. If the area of the small piston (A1) equals 10.5 cm2 and the area of the large piston (A2) equals 400 cm2, what force needs to be exerted on the small piston to lift the car?
1. List the given and unknown values. Given: F2 = 19,000 N
A1 = 10.5 cm2
A2 = 400 cm2
Unknown: F1
1 2
1 2
F F
A A 2 1
12
( )( )F AF
A
2
1 2
(19,000 N)(10.5 cm )
400 cmF
F1 = 500 N
Fluids in MotionFluids move faster through small areas than through larger areas, if the overall flow rate remains constant
Viscosity – the resistance of a gas or liquid to flow
Honey is more viscous than waterFluid pressure decreases as speed increases
EXIT SLIPWhat is buoyant force?
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