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PRENTICE HALL SCIENCE EXPLORER PHYSICAL SCIENCE CHAPTER 11 FORCES IN FLUIDS 11-1 Pressure Objectives: โข Tell what pressure depends on. โข Explain how fluids exert pressure. โข Relate how fluid pressure changes with elevation and depth A. What Is Pressure? 1. Pressure and Area a.) Pressure is defined as ___________________________________. b.) As area is __________________ the pressure ______________________. 2. Calculating Pressure a.) Pressure is calculated by dividing the total ___________ by the ________. ๐น๐น๐น๐น๐น๐น๐น๐น๐น๐น b.) ๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐๐ = ๐ด๐ด๐ด๐ด๐ด๐ด๐ด๐ด B. Fluid Pressure โ A fluid is a material that can easily __________________. 1. What Causes Fluid Pressure? a.) As particles in a fluid __________________ with their container and with objects in the fluid, they produce __________________. b.) All of the forces exerted by the individual particles in a fluid combine to make up the __________________ exerted by the fluid. 2. Air Pressure a.) __________________ is a fluid. b.) We live at the bottom of about ____________________________ of air. c.) Each cubic meter of air has a mass of about __________________. d.) The force with which air presses down on Earth and those objects on Earth is known as _____________________________. 3. Balanced Pressure a.) At sea level, air pressure is about __________________. b.) Fluid pressure is exerted equally in _________________________. c.) Also, pressure from fluids __________________ your body balance pressure from fluids __________________ your body. d.) If the air were removed from a can, the outside air pressure would ____________________ it. C. Variations In Pressure 1. Atmospheric Pressure and Elevation โ as you travel __________________ in altitude, air pressure __________________ explaining why your ears โpopโ. 2. Water Pressure and Depth a.) Water pressure __________________ as depth __________________s. b.) At 10 meters, the water pressure is __________________ atmospheric pressure. c.) The pressure at the bottom of the ocean (or any body of water) is the combined total of the __________________ and __________________ above that point. d.) In the deepest parts of the ocean, water pressure can reach __________________ that of air pressure. 3. Measuring Pressure a.) Atmospheric pressure can be measured with an instrument called a __________________. b.) Rapidly decreasing air pressure usually means __________________ is on the way. c.) Air pressure is expressed in several ways: i.) Normal air pressure is ____________________________________. ii.) Normal air pressure is ____________________________________. iii.) Normal air pressure is ____________________________________. 11-2 Floating And Sinking Objectives: โข Explain what the effect of the buoyant force is. โข Demonstrate how you can use density to determine whether an object will float or sink in a fluid. A. Buoyancy 1. Gravity and the Buoyant Force a.) __________________ is the ability to float. b.) Water and all other fluids exert an __________________ force on all objects submerged in them called the _____________________________. c.) The buoyant force acts in the __________________ direction as the force of gravity, so it makes an object feel lighter. d.) An object sinks if the force of __________________ (its weight) is greater than the __________________ force. 2. Archimedesโ Principle a.) Archimedesโ Principle states that the buoyant force acting on a submerged object is equal to the weight ______________________ the object displaces. b.) If the object weighs less than the weight of the fluid it displaces, __________________. c.) If the object weighs more than the weight of the fluid it displaces, __________________. B. Density 1. What Is Density? a.) The density of a substance is its __________________ per unit volume. ๐๐๐๐๐๐๐๐ b.) ๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท๐ท = ๐๐๐๐๐๐๐๐๐๐๐๐ 2. Comparing Densities of Substances a.) All __________________ have their own density. b.) The density of water is __________________. c.) Materials with lesser densities ___________________________ of material with greater densities. 3. Changing Density a.) Ice float because it has __________________ than water. b.) Submarines can __________________ their density in order to float or sink. 11-3 Pascalโs Principle Objectives: โข State Pascalโs principle โข Explain how a hydraulic system works. A. Transmitting Pressure In A Fluid 1. What Is Pascalโs Principle? a.) In the 1600โs French mathematician Blaise Pascal developed a principle that explains how pressure is _________________________ in a fluid. b.) Pascalโs __________________ is used for the SI unit of pressure. c.) Pascalโs principle states: When __________________ is applied to a __________________ fluid, the change in pressure is transmitted equally to all parts of the fluid. 2. Using Pascalโs Principle โ The ____________________________________ explained in Figure 15 on page 390 makes use of Pascalโs principle. B. Hydraulic Systems 1. A hydraulic system uses __________________ to transmit pressure in a confined fluid. 2. The hydraulic system multiplies __________________ by using the same pressure on a ___________________________. a.) ____________________________________ b.) ____________________________________ 11-4 Bernoulliโs Principle Objectives: โข Explain how, according to Bernoulliโs principle, fluid pressure is related to the motion of the fluid. โข List some of the applications of Bernoulliโs principle. A. Pressure And Moving Fluids 1. Fluid Motion a.) Fluids move from an area of ___________ to an area of ___________ pressure. b.) Removing ___________ from a straw causes the pressure exerted on the fluid in a drink to ____________________________________ the straw. 2. What Is Bernoulliโs Principle? a.) In the 1700โs Swiss scientist Daniel Bernoulli discovered that the pressure in a moving fluid was __________________ than that of a fluid sitting still. b.) Bernoulliโs principle states: As the speed of a moving fluid _______________, the pressure within the fluid __________________. B. Applying Bernoulliโs Principle 1. Objects in Flight a.) Airplane wings are designed with a _________________________ on top that is __________________ than the surface on bottom. b.) As the wing slices through the air, the air moving across the top of the wing must travel __________________ than the air moving across the bottom of the wing. c.) The decrease in pressure creates โ__________________โ on the wing. 2. Atomizers a.) In an __________________, air is squeezed past a tube that opens into a container of liquid. b.) The decrease in air pressure caused by the moving air causes the fluid to __________________ in the tube and be blown out. 3. Chimneys a.) As air moves outside the chimney, its pressure is __________________ than the still air __________________ the chimney. b.) The difference in pressure causes the __________________ in the chimney. 4. Flying Disks a.) A Frisbee uses the same principle as the __________________ to maintain flight.