recitation01

# recitation01 - is a better choice because it only requires...

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Figure 1: A typical manometer. The left side is exposed to the pressure that is to be measured, the right side is exposed to the atmosphere. Using the hydrostatic equation, the gage pressure can be measured. 1 Manometers at sea level 1.1 Water Height of the column: p - p = ρgL 10 kPa = ( 1000 kg / m 3 ) ( 9 . 8 m / s 2 ) L L = 10 kPa (1000 kg / m 3 ) (9 . 8 m / s 2 ) L = 1 . 02 m 1

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Accuracy/Precision/Gradations: 0 . 1 kPa = ( 1000 kg / m 3 ) ( 9 . 8 m / s 2 ) L L = 0 . 1 kPa (1000 kg / m 3 ) (9 . 8 m / s 2 ) L = 0 . 01 m = 1 cm Author’s note - when substituting values, please be very careful to carry units, show can- cellations, etc. I’ve found that checking units is a VERY good practice to get the students into. 1.2 Mercury Height of the column: p - p = ρgL 10 kPa = ( 13560 kg / m 3 ) ( 9 . 8 m / s 2 ) L L = 10 kPa (13560 kg / m 3 ) (9 . 8 m / s 2 ) L = 0 . 075 m Accuracy/Precision/Gradations: 0 . 1 kPa = ( 13560 kg / m 3 ) ( 9 . 8 m / s 2 ) L L = 0 . 1 kPa (13560 kg / m 3 ) (9 . 8 m / s 2 ) L = 0 . 0008 m = 0 . 8 mm If you have a lot of space, then a water manometer is a good choice because a 0.1 kPa diﬀerence is very easily read. If you do not have a lot of space, then a mercury manometer
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Unformatted text preview: is a better choice because it only requires a column of 7.5 cm. The absolute pressure measured is 111.325 kPa. 2 2 Manometers at 1400 m above sea level If the experiment takes place at 1400 m above sea level, with the same gage pressure, none of the heights will change. Because the height calculation is based on a pressure diﬀerence, it doesn’t matter what the reference pressure is, as long as the gage pressure remains the same. However, because the reference pressure changes, the absolute pressure will change to 95.6 kPa. 3 Fixed Column A water manometer with a 1 m high column can measure a pressure diﬀerence of: Δ p = ρgh = ( 1000 kg / m 3 ) ( 9 . 8 m / s 2 ) (1 m) = 9800 Pa A mercury manometer of the same height can measure a pressure diﬀerence of: Δ p = ( 13560 kg / m 3 ) ( 9 . 8 m / s 2 ) (1 m) = 132888 Pa 3...
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recitation01 - is a better choice because it only requires...

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