Question

The right-hand tube of the manometer is open to the atmosphere. The pump has been operated so that the mercury levels differ, as shown, by 250 mm. The density of mercury is 13 600 kg / m3. i) Calculate the pressure, in Pa, due to the 250 mm column of mercury.

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Answer 1

P(ressure) = d g h = density * gravity * height

P = 13600 * 9.8 * .25 = 33,300 Pa

Check: 1 atm = 76 cm = 760 mm height = 1.01 * 10E5 Pa

h = 1.01 * 10E5 / 9.8 * 13600 .758 m = 758 mm for 1 atm

250 / 758 = 1/3 atmosphere = 33,700 Pa close enough for estimates

(the pressure requested is 1/3 atmosphere where 1 atm = 760 mm Hg)