A barometer is used to measure air pressure. It is made of a tube of mercury (density of 13 500 kg/m3) in an open container. The top of the tube is sealed and contains a vacuum. The bottom is open to the air. During a storm, the mercury is observed to have a height of h = 0.70m. a) What is the air pressure during the storm? b) Mercury is dangerous! Suppose we decided to build a barometer using water (density of 1000 kg/m3) instead of mercury. What would be the height of the water during the storm?
Fluid Pressure
The term fluid pressure is coined as, the measurement of the force per unit area of a given surface of a closed container. It is a branch of physics that helps to study the properties of fluid under various conditions of force.
Gauge Pressure
Pressure is the physical force acting per unit area on a body; the applied force is perpendicular to the surface of the object per unit area. The air around us at sea level exerts a pressure (atmospheric pressure) of about 14.7 psi but this doesn’t seem to bother anyone as the bodily fluids are constantly pushing outwards with the same force but if one swims down into the ocean a few feet below the surface one can notice the difference, there is increased pressure on the eardrum, this is due to an increase in hydrostatic pressure.
A barometer is used to measure air pressure. It is made of a tube of mercury (density of 13
500 kg/m3) in an open container. The top of the tube is sealed and contains a vacuum. The
bottom is open to the air.
During a storm, the mercury is observed to have a height of h = 0.70m.
a) What is the air pressure during the storm?
b) Mercury is dangerous! Suppose we decided to build a barometer using water
(density of 1000 kg/m3) instead of mercury. What would be the height of the water during the storm?
The Hindenburg was an airship. It had a very large hydrogen-
filled balloon, with a volume of 140 000 m3. Below the balloon
were heavy engines and room for cargo.
The density of air is 1.20 kg/m3. The density of hydrogen is 0.09
kg/m3.
c) What was the buoyant force on the balloon?
d) What was the weight force of the hydrogen?
e) If the balloon didn’t accelerate up or down, what was the total mass of the engines and cargo?
Assume that the weight of the balloon fabric is negligible.
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