Pressure Questions
Below are a number of questions based on the work covered so far. I have split them into the corresponding sections.
Pressure
Q1) Express a pressure of 450mm of mercury in Pascals
Q2) The Mariana trench is located in the Pacific Ocean and has a depth of approximately 11 000m. If a diving chamber like the one below was to explore the bottom of the trench (to find odd creatures like the one shown) , what would the force be on the circular observation window (diameter = 20cm). The density of sea water is 1025 kgm -3 .
Q3) To try and get an idea of what this number means calculate how high a cylinder of Concrete (density = 2200kgm -3 ) of the same diameter would have to be in order to provide the same force if it were suspended by the window.
Q4)
A meat baster consists of a squeeze bulb attached to a plastic tube. When
the bulb is squeezed and released, with the open end of the tube under the
surface of the basting sauce, the sauce rises and can then be squirted over
the meat. If the water rises 15cm up the baster tube when tested;
a) What is the absolute pressure in the bulb?
(assume that the atmospheric pressure is 1.01 x 10
5
Pa)
b) If the device were taken up a mountain, would it work any differently.
If so explain why.
Q5) A mercury barometer reads 750mm on the top of a building and then when taken to the ground floor it reads 760mm. If the density of air remains at a constant 1.29 kgm -3 then what is the height of the building?
The continuity equation
Q6)
A
Patient recovering from surgery is being given fluid intravenously. The fluid
has a density of 1030 kgm
-3
and 9.5 x 10
-4
m
3
of it flow into the patient every six hours.
What is the mass flow rate in Kgs
-1
?
Q7)
A fire hose is connected to a fire hydrant. The hose has a radius of 0.020m.
Water enters the hydrant through an underground pipe of radius 0.080m. In
this underground pipe the water has a speed of 3ms
-1
.
a) What is the flowrate through the hose in kghr
-1
?
b) What is the water speed in the hose?
c) Do a) and b) again but this time imagine that there are three identical hoses attached to the hydrant.
The Bernoulli Equation
Q8) Prairie dogs are pretty clever animals. They seem to understand the Bernoulli equation without having to do all the maths! In order for them to survive in their burrows they create air circulation by making the entrances of their burrows different shapes. This changes the air speed over the entrances and thus creates a pressure difference that creates air flow. I told you they were clever.
If the air that flows over the entrances is of a constant density of 1.29 kgm -3 and the air speeds are as shown in the diagram above, what is the pressure difference between the two entrances.
Q9) Water flows down a hose with a speed of 0.500ms -1 . The hose has a radius of 0.020m and is horizontal.If the nozzle of the hose has and effective radius of 3.0 x 10 -3 m then at what speed does the water leave the hose?
Q10) If the water leaves the hose at atmospheric pressure, what is the pressure at the inlet end?