11.3 Pressure

11.3 Pressure

• The equation for gives is solved.

• The table has a density of water.

• There is a large amount of water.
• In this example, the weight of the water is where the Earth's gravity is.
• It's reasonable to ask if the dam can provide a force equal to the weight.
• The answer is no.
• The force of the dam can be smaller than the weight of the water it holds back.

• The world's largest hydroelectric plant was completed in 2008, generating power equivalent to 22 average-sized nuclear power plants.
• The concrete dam is 2.3 km across.
• This dam has a 660 km long reservoir.
• More than one million people were displaced by the creation of the dam.

• There are many examples of pressures in fluids.

• There is a force applied to an area.

• There are many other units for pressure that are used in the same way.

• millimeters of mercury (mm Hg) is used in the measurement of blood pressure, while pounds per square inch is used as a measure of tire pressure.
• When discussing fluids, pressure is important.

• The International Space Station has no atmospheric pressure.
• Her air tank has a pressure gauge.

• If we find the area acted upon, we can find the force exerted from the definition of pressure.

• The area of the end of the cylinder is given.

• The tank must be strong.
• The force exerted by a pressure is proportional to the area acted upon as well as the pressure itself.

• The end of the tank exerts force on its inside surface.
• The force is exerted by a static or stationary fluid.
• We have already seen that fluids can't exert shearing forces.
• The fluid pressure is a quantity.
• The forces due to pressure are always in a straight line.

• Swimmers and the tire feel the pressure.

• The tire's pressure exerts forces on all the surfaces it contacts.
• The directions and magnitudes of the forces are given by the arrows.
• Shearing forces do not exert static fluids.

• The swimmer is under pressure since the water would flow into the space he occupies if he were not there.

• The forces on the swimmer are represented by the arrows.
• The forces underneath are larger due to greater depth, giving a net upward force that is balanced by the swimmer's weight.

• As you change the volume, add or remove heat, change gravity, and more, you can see what happens when you put gas in a box.
• The properties of the gas vary in relation to each other, if you measure the temperature and pressure.

• If you've ever been on a plane or in a swimming pool, you've experienced the effect of depth on pressure in a fluid.
• The weight of air above you exerts air pressure on you at the Earth's surface.

• The weight of air above you decreases as you climb up in altitude.
• With increasing depth, the pressure on you increases.
• The pressure on you is caused by the weight of water above you and the atmosphere above you.
• If you notice an air pressure change on an elevator ride that transports you many stories, but you only need to dive a meter below the surface to feel a pressure increase, you're in good shape.
• Water is much denser than air.

• The weight of the fluid is supported by its bottom.
• The pressure on the bottom is determined by the weight of the fluid.

• The dimensions of the container are related to the volume of the fluid.

• The pressure is the weight of the fluid.
• The equation has general validity beyond the special conditions.
• The surrounding fluid kept the fluid static even if the container weren't there.
• The equation shows the pressure due to the weight of the fluid at any depth below its surface.
• This equation holds great depths for liquids, which are nearly incompressible.
• One can apply this equation if the density changes are small over the depth considered.

• The weight of the fluid is supported by the bottom of the container.
• The bottom must support the fluid since the vertical sides can't exert an upward force.

• Pressure and force will be considered on the dam retaining water.
• The water is 80.0 m deep at the dam, which is 500 m wide.

• The pressure at the average depth of 40.0 m is the average due to the weight of the water.

• The value has already been found.

• The force is small compared to the weight of the water in the dam.
• It depends on the average depth of the dam and the width and length of the lake.
• The force is dependent on the water's average depth and the dimensions of the dam.
• In the diagram, the thickness of the dam increases with depth to balance the increasing force due to the increasing pressure.

• The dam must be able to hold onto the water.
• The force is small compared to the water behind the dam.

• The weight of air above a given height is what causes atmospheric pressure.
• The atmospheric pressure at the Earth's surface varies a little due to the large-scale flow of the atmosphere.

• The average weight of a column of air above the Earth's surface is equivalent to.

• The average density of the atmosphere is 120 km.
• Compare this density with the air listed in the table.

• We have to be atmospheric pressure, given, and known, and so we can use this to calculate.

• The average density of air between the Earth's surface and the top of the Earth's atmosphere is 120 km.
• Table 11.1 shows the density of air at sea level.
• The density of air is the highest near the Earth's surface and plummets with altitude.

• The pressure of the water is equal to 1.00 atm.