Question

You wish to observe the progress of your vacuum pump in evacuating a tall bell jar for the purpose of demonstrating that sound waves do not travel in a vacuum. So you place a mercury barometer inside the bell jar and follow the height of the mercury column as the pump chugs away. When you observe a height of 5.67 mm, what fraction of atmospheric pressure, expressed as a percentage, have you achieved in your bell jar? The density of mercury is 1.36 × 104 kg/m3 and standard atmospheric pressure is 1.01 × 105 Pa.

Answer 1

Here ,

final height of mercury, hf = 5.67 mm

at the atmospheric pressure ,

height of mercury , h = 760 mm

Now ,

fraction of atmospheric pressure of this pressure = hf/h * 100

fraction of atmospheric pressure of this pressure = 5.67 *100/760 %

fraction of atmospheric pressure of this pressure is 0.746 %

the fraction of atmospheric pressure of this pressure is 0.746 %