Herriman High AP Physics 2 Chapter 9 Solids and Fluids

Herriman High AP Physics 2 Section 9.3: Density and Pressure

Herriman High AP Physics 2 Density

Herriman High AP Physics 2 Pressure Units Atmospheres (atm) Pascals (Pa) aka N/m 2 1 atm = 1.01x10 5 Pa

Herriman High AP Physics 2 Fluids Fluids exert pressure in all directions Fluids always exert pressure perpendicular to any surface that it contacts.

Herriman High AP Physics 2 Sections 9.4 & 9.5: Pressure varies with depth All points at the same depth in a fluid should be at the same pressure (as long as the fluid is at rest) ΔP is called the gauge pressure P is the absolute pressure P 0 is the pressure at height 0

Herriman High AP Physics 2 Sample Problem In a huge oil tanker, salt water has flooded to a depth of 5 meters. On top of the water is an oil layer 8 meters deep. The oil has a density of 0.7 g/cm 3 and the salt water has a density of kg/m 3. Find the pressure at the bottom of the tank.

Herriman High AP Physics 2 Section 9.6: Buoyancy & Archimedes’ Principle Archimedes Principle – Any body completely or partially submerged in a fluid is buoyed up by a force whose magnitude is equal to the weight of the fluid displaced by the body. This force is called a buoyant force.

Herriman High AP Physics 2 Helpful hints for buoyancy The Volume V given in the buoyancy equation is only the volume of the object that is submerged in the fluid. If you need to find the volume of the submerged portion of the object you may use the ratio below.

Herriman High AP Physics 2 Section 9.7: Fluids in Motion Fluid Flow Continuity Bernoulli’s Equation

Herriman High AP Physics 2 Flowing Fluids Characterized in two ways: Laminar (Streamline) flow –Every particle flows along a straight line Turbulent –Has eddy currents Note: We will only deal with Laminar Flow

Herriman High AP Physics 2 Ideal Fluids Nonviscous Incompressible Motion is steady Moves without turbulence

Herriman High AP Physics 2 Equation of Continuity The flow rate of every point in a pipe is uniform The amount of mass flowing through each point is the same

Herriman High AP Physics 2 Sample Problem Each second, 5,525 m 3 of water flows over the 670 m –wide cliff of the Horseshoe Falls portion of Niagara Falls. The water is approximately 2 meters deep as it reaches the cliff. Estimate its speed at that instant.

Herriman High AP Physics 2 Bernoulli’s Equation A fluid moving through a pipe will have changing pressure if the pipe area or elevation changes A faster moving fluid means a lower pressure A slower moving fluid means a higher pressure

Herriman High AP Physics 2 The Equations

Herriman High AP Physics 2 Hints for problems Specific Gravity 1 mL = 1 cm 3 Rate of flow is usually given in volume/time Speed is given in length/time Therefore dividing the flow rate by the area it flows out of will give you the speed

Herriman High AP Physics 2 Sample Problem A near-sighted sheriff fires at a cattle rustler with his trusty six-shooter. Fortunately for the rustler, the bullet misses him and penetrates the town water tank, causing a leak. If the top of the tank is open to the atomosphere, determine the speed at which the water leaves the hole when the water level is 0.5 meters above the hole. Where does the stream of water hit the ground if the hole is 3 meters above the ground?