
Pressure
Question: pressure...? A scientist builds a pressure thermometer by sealing air in a tank. If the pressure inside the tank is 945.6 mmHg when it is placed in a hot water bath at 92oC, and 653.0 mmHg when left on the ground outside the laboratory, what is the Celsius temperature outside the lab?
Answer: T1/P1 =T2/P2
T2 =( T1/P1) x P2, T1=273 +92 = 365 K, P1= 945.6 mmHg
P2 = 653.0 mmHg
T2 = (365/945.6)x653.0 = 252.1 K
t2= 252.1 273 = 20.9 oC
Question: How much pressure is due to water vapor and how much to the pressure of oxygen? The vapor pressure of water at 21 degrees Celsius is 19 mmHg. If 100ml of oxygen is collected over water at 21 degrees Celsius and 730 mmHg total pressure, how much pressure is due to water vapor and how much to the pressure of oxygen?
Answer: The total pressure is simply the sum of all the partial pressures inside the system.
730mmHg = 19mmHg (from water) + 711 mmHg (from oxygen).
Question: What physically causes gas pressure and how can you increase the pressure of gas? Also, I have a few other questions that I would like answered too :) Thanks for all your help.
1. How do temperatures in Celsius and Kelvin differ in their relationship with pressure?
2. How do you write an equation to express the relationship between pressure and temperature (K). Use symbols P, T, and c.
3. What should happen to the pressure of gas if Kelvin is doubled?
4. What shoul be the pressure at "absolute zero"
Thanks!
Answer: the gas law you can use is P1 * V1 = P2 * V2
T1 T2
(that's divided by)
you can increase gas pressure by reducing the volume which the gas occupies (P1 *V1 = P2 * V2 of the same gas) while the temperature remains the same
and also by reducing the temperature, while the volume remains the same
this temperature (T1 and T2) is ALWAYS measured in Kelvins, so if you were to use degrees C, you have to add 273 to the figure to make it into Kelvins. I hope that answers no 2
if the temperature is doubled then it follows that the Pressure will also double (if the volume is kept the same) so that the equation written previously to be proven.
I HOPE THAT HELPS!
Question: What would happen to the gas pressure inside the cylinder? Assume that you have a cylinder with a movable piston. What would happen to the gas pressure inside the cylinder if you decrease the volume of the gas to one third of the original volume?
(a) The pressure would decrease by one third as well.
(b) The pressure would be unchanged
(c) The final pressure would be three times of the initial pressure.
(d) The final pressure would be nine times of the initial pressure.
Answer: You have a confined gas in a cylinder with a movable piston. The gas will follow the combined gas law: P1V1/T1 = P2V2/T2.
Since there is no mention of changes in T, we will assume that T remains constant. Then the gas follows Boyle's law. Solve for the new pressure, P2.
P2 = P1V1/V2 = P1 x V1 / (1/3V1)
P2 = 3P1
The new pressure will be three times the original pressure. Therefore your answer is (C).
============== Follow up =============
(D) is definitely NOT the correct answer.
Question: What is the difference between hydrostatic and hydrodynamic pressure? I know hydrostatic pressure is basically the pressure due to the weight of the water (pressure= density*gravitational acceleration*height).
One online definition of hydrodynamic pressure says that it is the difference between the pressure of the fluid and the hydrostatic pressure. Isn't the pressure of the fluid the SAME THING as the hydrostatic pressure?
Ok. I would like a verbal and mathematical definition (like what's the equation) of hydrodynamic pressure.
Answer: Hydrostatic pressure is due to the weight of the fluid. For example, if you put a cheap watch (or an expensive one) at the bottom of the Mariana Trenches, the hydrostatic pressure will force the water in through the seals.
Dynamic pressure is in connection with an airplane flying and so on. Airplanes actually used pitot tubes to measure their airspeed. A pitot tube measures the difference between dynamic pressure and stagnation pressure. It is very difficult to explain without a picture. The basic idea is derived from Bernoulli's equation. Bernoulli's equation can be modified to show that in the pitot tube, when the speed increases the pressure decreases. This actually has huge physical implications and it is the basis for the atomizer and the airfoil. If you want to see this illustrated, grab a sheet of paper and put it on a table. Create a small arch, about an inch above the table, and about half an inch wide. Keep the rest of the paper flat on the table. Now blow through the hole. You can even do this with an aerosol can or an air compressor, you will see that contrary to intuition, the sheet will contract, it will NOT expand. This is because the velocity of the fluid went up inside the sheet, so the dynamic pressure goes down, then the hydrostatic pressure will crush it.
Question: What prevents the pressure from increasing as a cloud contracts due to its gravity? A) Excess pressure is released in jets of material from the young stars.
B) As the cloud becomes denser, gravity becomes stronger and overcomes the pressure buildup.
C) Once the cloud reaches a critical density, the pressure becomes degenerate and independent of temperature.
D) The pressure is transferred from the center of the cloud to its outer edges where it can dissipate.
E) Thermal energy is converted to radiative energy via molecular collisions and released as photons.
Answer: B) is the only answers which is correct, the other answers seem to go against elementary physics laws.
Question: Why is my pool pump pressure so high? My pool pump pressure seems unreasonably high. The pressure gauge on the filter indicates about 22 psi normally and 28 psi when running the solar. I have a 4.9 sq foot sand filter. The pressure doesn't change by more than one psi after backwashing.
On the pressure side of the pump the water moves to the filter, then to a Zodiac Duoclear salt cell (with integrated mineral filter), then the solar control valve, then out to two pool returns (about 40 feet away) over 2 inch PE flex piping.
A friend of mine has a similar system and his pressure seems to be about half of what mine is. I've checked that the gauge is not stuck and it goes all the way to zero when the system is shut off. Any suggestions?
Answer: It sounds like your back washing is working. It drops so little because it didn't need back washing. Your solar seems to be in reasonable limits, so the only thing left is your Zodiac salt cell. Bypass that to see if that corrects the problem. Likely so.
Question: What happens to pressure of a gas inside a container if the temperatur of the gas decreases? is it
a) the pressure cannot be predicted
b) the pressure decreases
c) the pressure increases
d) the pressure does not change
Answer: As temperature increases, so does pressure and vice versa.
PV/T is constant.
Therefore as your temperature goes down, so does the pressure.
b) is definitely your answer.
Question: Which pressure washer should I buy to use around the yard? I've looked at a few websites and see that I can get gas powered washers for upwards of $400 and also get small electric ones for as low as $80. I understand that the big difference seems to be the pressure that each puts out (PSI) but that's all I understand.
Can I get a compressor so I can say attach a paint sprayer, a tire inflator and then attach a head so I can pressure wash? Or do I have to get a compressor for paint and air and then a pressure washer as well? I'm mostly interested in the washing part but would be nice to have an all in one solution if that is even available?
Here is what I want to do...wash the cars, RV, kids bikes, driveway, vinyl siding on the house and basic yardwork type of chores.
Please help me figure out what to buy?
Answer: If it were me... I'd go to the local rental equipment shop and ask the guy in charge of what he thinks. Why  because he would be the one very familiar with what you'd be looking for. As that's what he rents, and is very knowledgeable about.
Question: What is the pressure in Pa inside a container? What is the pressure in Pa inside a container if the mercury level in the manometer arm attached to the container stands 18.5cm higher than the mercury level in the manometer arm that is open to the atmosphere? The atmospheric pressure as determined by a barometer is 103,000 Pa.
I know that the pressure inside a container has to be lower than 103,000 Pa, since the mercury level in the arm attached to the container is higher, meaning the atmosphere is pushing much harder.
And I have to use the formula:
pressure in container=height difference + atmospheric pressure.
So, I converted 18.5mm into 2466.46 Pa, then added to the 103,000. The answer, then, is 105466.4638. I don't think this is logical, because now, the pressure inside the container is higher, where it should be lower.
How would you solve this problem?
Should the formula be
pressure in container=atmospheric pressure  height difference?
Answer: Youir logic is perfect except that the height here is viewed as negative like you said since the external arm is lower.
So 103Kpa  2.47Kpa =
Good job of thinking about the answer before solving  it will always benefit you!
Question: My water pressure is very low in my home. What are the possible fixes? At the point where the water enters my home, there are no pressure adjustment valves. The pressure throughout our area is also low. I am thinking about adding a booster pump. Does anyone have experience with the addition of a booster pump to an existing city water line inside the house to raise the overall pressure?
Answer: You need to explore the reason for the low pressure. A cheap pressure gage connected to a hose bib can tell you if the pressure provided is low, or if the pressure drops rapidly when water is flowed in the house. One could expect the nonflowing (static) pressure to drop only slightly when a faucet is opened. If the static pressure is low to begin with, and doesn't drop a lot when water is flowed, a pump will help. If the static pressure is acceptable but there is a considerable drop when a faucet is opened, the pump will not do the job. This would indicate a very long line into the house, too small pipe in the line to the house, an obstruction in the pipe, or a partially closed valve.
Question: What is the difference between water pressure and air pressure? Basically I want to know if pressure is equal no matter what type of pressure it is. I've heard that 100 pounds of air pressure is like 400 pounds of water pressure (when used in piping).
Will a pipe rated for 300 pounds of water pressure hold up to 300 pounds of air pressure? I am having a disagreement with some guys at work about this, so if you have a source to go with the answer that would be great!
Answer: Water is incompressible. As soon as a water pipe cracks a little, the pressure drops instantly. When you have a compressed gas in a pipe and the pipe fails, the gas can expand and still provide pressure to the pipe fragments. Failures under these circumstances are much more dangerous.
Note that a small leak in a hydraulic line can still shoot a jet an oil through you.
Question: what happens to the pressure if the temperature in K is doubled? Can somebody please explain these to questions to me?
3) Consider the following changes imposed upon a sample of gas, assuming the variables not mentioned remain constant:
a. what happens to the pressure if the temperature in K is doubled?
b. What happens to the volume if the pressure is tripled?
c. What happens to the volume if the temperature decreases from 300K to 200K?
4) At sea level we are under 15.8 pounds of pressure per square inch of our body. This is the equivalent of a 16 pound bowling ball at every inch of our body. Describe why we are not overcome by the pressure of the atmosphere? What experiment in our course relates to this concept?
Answer: if you assume the gas is ideal...
P1V1 = nRT1
P1V1/T1 = nR
P2V2 = nRT2
P2V2/T2 = nR
P1V1/T1 = P2V2/T2
*** question 3 ***
a)
P2 = P1V1T2 / T1V2
if V is constant, ie V1 = V2 = V
and if T2 = 2xT1
P2 = P1 x 2 x T1 x V / T1V = 2 x P1... ie pressure doubles
b)
P1V1/T1 = P2V2/T2
V2 = P1V1T2/T1P2
T is constant, P2 = 3 x P1
V2 = P1 V1 T / 3P1T = 1/3 V1. volume is reduced to 1/3 of original volume
c)
P1V1/T1 = P2V2/T2
V2 = P1V1T2/T1P2
P1 = P2 = P,
V2 = V1 x 200K / 300K = 2/3 V1
*** question 4 ***
we are predominantly solids and liquids. solids and liquids are not very compressible
Question: How can you determine pressure altitude without setting the altimeter? I already saw an answer about pressure altitude but for some reason, i just still don't get the relationships. How does the actual barometric pressure reading given relate to pressure altitude, is it the same thing? Can you figure out pressure altitude without using the altimeter setting in a plane? I'm missing something and just can't seem to get it straight.
Answer: First, pressure altitude is used as an indicator for atmospheric pressure. As you probably know this and temp are used to calculate aircraft performance. If you want to know the pressure altitude without being in the plane or you just don't want to set it in the Kollsman window,then do the following: 1. Request the local barometric altimeter setting, let's say it's 28.00 "Hg.
2. Take 29.92 "Hg (standard atmosphere) and substract minus the 28.00"Hg. (29.92"Hg28.00"Hg=1.92"Hg)
3. 1.92"Hg is the difference in pressure.
4. Take into account that each inch is worth 1000 ft.
5. Multiply 1.92"Hg X 1,000= 1,920 ft
6. The barometric setting (28.00) was less then 29.92, so we substract (we'd add if it was greater)1,920 from the present altitude of the aircraft.
7. Let's say we're at 10,000 ft;10,0001,920=8,080 ft
8. 8,080 is your pressure altitude!!!
But what does this mean??
It means that on a standard day (15C29.92 "Hg pres), you being at 10,000, really feels like 8,080 to the aircraft in regards to performance. It's basically just a way to put pressure into performace computations. I hope this answers it. Pressure altitude setting, 29.92"Hg is also used by aircraft above 18,000 ft at all times to provide aircraft separation.
Question: What is the osmotic pressure and molar concentration? A)Isotonic saline solution, which has the same osomotic pressure as blood, can be prepared by dissolving 0.923g of NaCl in enough water to produce 100mL of solution. What is the osmotic pressure of this solution at 25C ?
B)Osmosis is the process responsible for carrying nutrients and water from groundwater supplies to the upper parts of trees. The osmotic pressures required for this process can be as high as 18.1atm . What would the molar concentration of the tree sap have to be to achieve this pressure on a day when the temperature is 25C?
Answer: Use this equation, osmotic pressure = CRT,
where C is the concentration in molarity, R is the gas constant, and T is the temperature in Kelvin. So, the answers to your problems are:
A) osmotic pressure = CRT
to get C, get the number of moles of NaCl then divide it with volume of the solution
mole NaCl = 0.923g / 58.442 g/mol
mole NaCl = 0.0158 mol
C = 0.0158 mol / 0.1L
C = 0.158 mol/L
So,
osmotic pressure = 0.158 mol/L*(0.082058 Latm/molK)*(25+273K)
osmotic pressure = 3.86 atm
B) C = osmotic pressure / RT
C = 18.1 atm / (0.082058 Latm/molK * 298K)
C = 0.740 mol/L
Question: How much tire pressure should there be in 2007 toyota corolla? What is the correct amount of air pressure for the tires of a corolla? it has been over 4 months, i haven't added any air to the tires. the tires are of good year. I heard somewhere that the air pressure of a full sized sedan is 35 psi. So since corolla is not full size sedan and is smaller, the air pressure i presume would be less than 35 psi. But not sure what the figure is.
Answer: 2007 Toyota corolla
I have the same car the the rite exact tire pressure is 32 psi
I face the same problem last month with the pressure
GOOD LUCK WITH YOUR CAR
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