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Pgs. 317 - 342.  Calculate the pressure exerted by a fluid.  Explain Pascal’s Principle.  Calculate how pressure varies with depth in a fluid.

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Presentation on theme: "Pgs. 317 - 342.  Calculate the pressure exerted by a fluid.  Explain Pascal’s Principle.  Calculate how pressure varies with depth in a fluid."— Presentation transcript:

1 pgs. 317 - 342

2  Calculate the pressure exerted by a fluid.  Explain Pascal’s Principle.  Calculate how pressure varies with depth in a fluid.

3  A measure of the force applied to a surface per unit area  SI unit of pressure is the Pascal (Pa) = 1 N/m 2

4  The pascal is a small amount of pressure  At sea level, the pressure of the atmosphere is 1.01x 10 5 Pa  This amount of air pressure is the basis for another unit, atmosphere  1 atm = 1.01 x 10 5 Pa

5  Atmospheric pressure is normally about 100,000 Pascals.  Differences in atmospheric pressure cause winds to blow.  Low atmospheric pressure inside a hurricane’s eye contributes to the severe winds and the development of the storm surge.

6  The force on a surface caused by pressure is always normal (or perpendicular) to the surface. This means that the pressure of a fluid is exerted in all directions, and is perpendicular to the surface at every location.

7  Calculate the net force on an airplane window if the cabin pressure is 90% of the pressure at sea level and the external pressure is only 50% of that at sea level. The window is 0.43m tall and 0.30m wide.

8  Applied pressure is transmitted equally throughout a fluid

9

10 The small piston of a hydraulic lift has an area of 0.20 m 2. A car weighing 1.20 x 10 4 N sits on a rack mounted on the large piston. The large piston has an area of 0.90 m 2. How large a force must be applied to the small piston to support the car?

11  P = ρgh P: pressure (Pa) ρ : density (kg/m3) g: acceleration constant (9.81 m/s2) h: height of liquid column (m)  This type of pressure is often called gauge pressure. Why?  If the liquid is water, this is referred to as hydrostatic pressure.

12  Absolute pressure is obtained by adding the atmospheric pressure to the hydrostatic pressure.

13  Pressure varies with the depth of a fluid  P o = 1.01 x 10 5 Pa

14  Buoyant forces arise from the differences in fluid pressure between the top and bottom of an immersed object.  P net = P bottom - P top

15  Atmospheric pressure is pressure from above  The weight of the air in the upper portion of Earth’s atmosphere exerts pressure on the layers below  Mercury barometer is commonly used to measure atmospheric pressure

16 Calculate the absolute pressure at an ocean depth of 1.00 x 10 3 m. Assume that the density of the water is 1.025 x 10 3 kg/m 3 and that P 0 = 1.01 x 10 5 Pa.


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