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?