Measuring pressure. Aims Describe the simple mercury barometer and its use in measuring atmospheric...
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Transcript of Measuring pressure. Aims Describe the simple mercury barometer and its use in measuring atmospheric...
![Page 1: Measuring pressure. Aims Describe the simple mercury barometer and its use in measuring atmospheric pressure Use and describe the use of a manometer.](https://reader036.fdocuments.us/reader036/viewer/2022062417/551b00255503462e578b5170/html5/thumbnails/1.jpg)
Measuring pressure
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• Aims• Describe the simple mercury
barometer and its use in measuring atmospheric pressure
• Use and describe the use of a manometer
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The manometer• A manometer measures pressure
difference.
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Atmospheric pressure
• Gasses are also fluids• The atmosphere is made of gasses• The atmosphere exerts a pressure• Equal to
• Density changes so must use average
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Using atmospheric pressure
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Pressure from the air
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The mercury barometer
• Torricelli filled a tube with mercury and inverted it into an open container of mercury. • Air pressure Po acting on the mercury in the dish can support a column of mercury 76 cm in height.
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Standard atmospheric pressure
The pressure that will support a column
of mercury of 760.0 mm heigh is known
as standard atmospheric pressure or
1 atmosphere (1 atm).
1 atm = 76 cmHg = 1.013 x 105 Pa = 103 millibar (mb)
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Pressure from the air
• As the air is removed from the inside the external pressure crashes the can.
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Uses of pressure in fluids
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Hydraulic jack
• The hydraulic press is an important application of Pascal’s Principle.
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Hydraulic Brakes
1. Brake pedal.2. Master cylinder.3. Break fluid.4. Slave cylinder.5. Large piston.6. Brake disc.7. Tyre.
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Why are the walls of a dam wider at the bottom than at the top?
A. It is cheaper to build
B. Gravity increases with depth
C. Pressure increases with depth
D. Looks nice
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A pressure of 600 Pa acts over an area of 2m2. What force creates this pressure?
A. 1 200 N
B. 300 N
C. 1 200 Pa
D. 300 Pa