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Chapter 13. 0. Fluids. 13 Fluids. Slide 13-2. Slide 13-3. Slide 13-4. Slide 13-5. Reading Quiz. The SI unit of pressure is N kg/m 2 Pa kg/m 3. Slide 13-6. Answer. The SI unit of pressure is N kg/m 2 Pa kg/m 3. Slide 13-7. Reading Quiz.
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Chapter 13 0 Fluids
13Fluids Slide 13-2
Reading Quiz • The SI unit of pressure is • N • kg/m2 • Pa • kg/m3 Slide 13-6
Answer • The SI unit of pressure is • N • kg/m2 • Pa • kg/m3 Slide 13-7
Reading Quiz • Gauge pressure is true pressure. Explain. • larger than • smaller than • the same as • None of the above Slide 13-8
Answer • Gauge pressure is true pressure. Explain. • larger than • smaller than • the same as • None of the above Slide 13-9
Reading Quiz • The buoyant force on an object submerged in a liquid depends on • the object’s mass. • the object’s volume. • the density of the liquid. • both B and C. Slide 13-10
Answer • The buoyant force on an object submerged in a liquid depends on • the object’s mass. • the object’s volume. • the density of the liquid. • both B and C. Slide 13-11
Density Slide 13-12
Pressure The pressure of the water behind each hole pushes the water out. The SI unit of pressure is 1 pascal = 1 Pa = 1 N/m2. Slide 13-13
Pressure in a Liquid Increases with Depth Slide 13-14
Example Problem In a graduated cylinder, 10 cm of oil (ρ = 0.85 g/cm3) floats on top of 20 cm of water (ρ = 1.00 g/cm3). What is the pressure at a height of 10 cm from the bottom of the cylinder? Slide 13-15
Atmospheric Pressure patmos = 1 atm = 103,000 Pa Slide 13-16
3 Example Problem The gas in the cylinder is at a pressure of pgas = 3.0 x 105 Pa. How high is the column of mercury? Slide 13-18
The Barometer Slide 13-19
Pressure Units Slide 13-20
Buoyancy Slide 13-21
Floating When the object sinks to the point that the weight of the displaced fluid equals the weight of the object, then the forces balance and the object floats in equilibrium. No net force. The volume of fluid displaced by a floating object of density o and volume Vo is The density of ice is 90% that of water. When ice floats, the displaced water is 90% of the volume of ice. Thus 90% of the ice is below water and 10% is above. Slide 13-23
How a Boat Floats Slide 13-24
Checking Understanding • Two blocks of identical size are submerged in water. One is made of lead (heavy), the other of aluminum (light). Upon which is the buoyant force greater? • On the lead block. • On the aluminum block. • They both experience the same buoyant force. Slide 13-25
Answer • Two blocks of identical size are submerged in water. One is made of lead (heavy), the other of aluminum (light). Upon which is the buoyant force greater? • On the lead block. • On the aluminum block. • They both experience the same buoyant force. Slide 13-26
Checking Understanding • Two blocks are of identical size. One is made of lead, and sits on the bottom of a pond; the other is of wood and floats on top. Upon which is the buoyant force greater? • On the lead block. • On the wood block. • They both experience the same buoyant force. Slide 13-27
Answer • Two blocks are of identical size. One is made of lead, and sits on the bottom of a pond; the other is of wood and floats on top. Upon which is the buoyant force greater? • On the lead block. • On the wood block. • They both experience the same buoyant force. Slide 13-28
Checking Understanding • A barge filled with ore floats in a canal lock. If the ore is tossed overboard into the lock, the water level in the lock will • rise. • fall. • remain the same. Slide 13-29
Answer • A barge filled with ore floats in a canal lock. If the ore is tossed overboard into the lock, the water level in the lock will • rise. • fall. • remain the same. Slide 13-30
Example Problem A block of plastic floats in water. 20% of the block’s volume is above the waterline. What is the density of the block? Slide 13-31
Example Problem A ball weighing 1.0 N has a density 1/3 that of water. What is the tension in the string when the ball is held under water as shown? Slide 13-32
Constrained Flow: Continuity Slide 13-33
Acceleration of Fluids Slide 13-34
Pressure Gradient in a Fluid Slide 13-35
Bernoulli’s Equation Slide 13-36
Example Problem In an agricultural irrigation system, water is pumped through a constant-diameter pipe up a 1.5-m-high embankment, where it empties into a field. If the farmer wants to pump water at a rate of 20 L/s, what pressure does his pump need to apply at the bottom of the pipe? Slide 13-37
Viscosity Slide 13-38
Poiseuille’s Equation Slide 13-39
Example Problem A garden hose is 10 m long and has an inner diameter of 2.5 cm. Using this hose it takes 5.0 s to fill a 10 L bucket. What is the water pressure at the spigot end of the hose? Slide 13-40
Summary Slide 13-41
Summary Slide 13-42