Water and oil are in a tank, calculate pressure at the bottom
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- เผยแพร่เมื่อ 14 มี.ค. 2014
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Fluid Mechanics Tutorial: Water and oil are in a tank, calculate pressure at the bottom
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Nice and easy to understand explanation, thanks 👍
Excellent! Can you please show how to calculate horizontal pressures at various depths when using oil and water?
How would you find the force on the sides of the container. Would you need to integrate and add the oil then the water. Or there a specific way to do so?
Thank you ❤️
Make more videos like this please
if the shape of the tank was not constant how would that affect the pressure ? like lets say it was a square then a cylinder?
could you tell me what is formula when we measure interface level by displacer type level transmitter?
how to calculate gauge pressure if same built question
If the tank is full and covered with a lid , will Patm be zero?
nice video - the result given would be in absolute pressure of course (not gauge pressure) just for peoples reference
what is the pressure head base of a 70foot tank fill to the top
310.1538 kPa
Does a water density in the middle of water (height 1.25 m) is less then density at the bottom? I mean water density is not const., but the difference is so small so we ingore it? Because density also depends on pressure, not only by temperature.
This video is at a 1st/2nd year (freshmen/sophomore) level. Take density of the fluid to be constant at all depths.
yeah bruh I think this is for ap physics students like myself, not fully fledged engineers with a professional degree
Why applying Patm ? I mean it surrounds the whole tank so its effet cancels itself no ?
The tank is only open to the atmosphere are the top
in the equation p1 = p0+ pgh how come you need to add the p0 into it?
As you go deeper into a fluid, the pressure increases. But it's relative. The increase is from the higher point to the lower point. The surface of the uppermost point is in contact with the atmosphere and therefor experiences atmospheric pressure. So if the increase in pressure as we go deeper into the fluid is relative to the top pressure we need to add the increase to the value of the top pressure. P0 in this case is Patm, so that's why we initially add the 101kPam. Should note that we're talking about absolute pressure here. Hope that helps to clarify
how would you find the force on the bottom of the tank in N?
Pressure = force * area. You know the pressure and area, so can just rearrange for force. This would basically be the weight of the water.
Would this be set up differently if the tank was a cylinder with a specific diameter?
Yes, it’s weird but true
Thanks
Only force of that pressure will depend on diameter (area)
Is there any pressure difference between closed and open water tank which is full of water?
I beleive so, when tank is closed you don’t need to factor in atmospheric pressure.
What is the pressure at the interference of these two fluids
Take it as equal to P1 = 112.7 kPa absolute.
What is the actual value of atmosphere pressure? 101kPa or 101325Pa? I'm confuse
101kPa is just rounded, 101,325 Pa = 101.325 kPa, but it's common in first year classes to round down simply to 101kPa (101,000 Pa) for atmospheric pressure. Check the expectations of your textbook or professor for which value they want you to use.
Sir What is the instance when patm is not considered??
If no part of the fluid column is exposed to the atmosphere. It could be possible in a manometer type setup where a piston is acting on one end of the the fluid and a known pressure is in the bulb on the other side. I've got a few videos on manometers here: th-cam.com/play/PLOAuB8dR35oeOIPMOBH6hjwobuIJHPKSN.html but all of them involve Patm.
If pressure at atm was zero this would totally change your answer right? Don't you usually assume Pressure of atm to be zero?
Thanks. Great video!!
jruby805 Hey I think you are getting gauge pressure and absolute pressure mixed up. Its all a matter of where you define your "zero point" when talking about gauge pressure. Absolute pressure is literally how much pressure you have compared to a perfect vacuum. If you are experiencing "0 kPa absolute" then you are probably in space. If you are experiencing "101 kPa absolute" then you are probably standing outdoors around sea level. A pressure of "0 kPa gauge" would mean that you have the same pressure as the reference pressure that you defined as your zero for this particular measurement. If you define atmospheric pressure as your reference, then a gauge pressure of 0 kPa would = Patm = "101 kPa absolute". The pressure at the bottom of the tank in this video is "137 kPA absolute", or could be "36 kPa gauge" if you defined atmospheric pressure as your reference aka "0 kPa gauge" (because 137-101=36). I made another video explaining the difference between gauge and absolute pressure, you can see it here: th-cam.com/video/oOMzRzpNBEE/w-d-xo.html Hope that helps clear it up!
Engineer4Free ahhhhhhhhh. Man, you're good. Thanks for clearing that up. You have no idea how such a big help this was!! Thank you so much!! And thanks for the other video, will check it out right now!!
In other words gauge pressure means that you should ignore the atmospheric pressure and focus on the system
Damn, it's really the little things that suddenly cause things to click. You saying that SG of 0.8 means it will be 80% as dense as water suddenly made specific gravity fall into place for me.
Awesome, glad I could help you get that! Stuff can seem more complicated than it actually is.
What if there is a mixer in the tank, is it still the same calculations ?
you should know density of mixer
@@pradipbehera4191 no u should know the density of the mixture formed, not the steel mixer
@@ashthepokemonmaster2375 u want to say still mixer . It doesn't mean anything. Fluids having different density don't mix each other just like explained in given video ,u may take example of oceans junction (central indian triple junction). It don't mix in horizontally also...
What if the container is closed at the top?
only "Po" ie (the pressure due to atm) wont affect anymore, rest stays the same
the only thing that will happen is that p knot will become zero
Why oil has higher density than water? Pls reply me. We know that an object with high density sink. (sorry bad englishg
The oil in this video has Specific Gravity (SG) = 0.8 which means it is equal to only 80% of the density of water. That's why the oil is on top and the water is below in this case, because the water has a higher density than oil, not the other way around.
so the pressure at the bottom is P2 or P1+P2 could u tell me ?
The pressure at the bottom = P2. P2 = Patm + ρgh {oil} + ρgh {water}.
@@Engineer4Free So what if they ask for the gauge pressure at the bottom ?
@@junghoainam21 the absolute pressure at the bottom is P2 = 137kPa. Gauge pressure = absolute pressure - atmospheric pressure, so the gauge pressure at the bottom is 137 kPa - 101 kPa = 36 kPa
@@Engineer4Free gauge pressure = absolute pressure - atmospheric pressure? Isn't the pressure on the top of water is that pressure of oil?
P.s. Just clarifying. Hehe
What if the tank is elevated?
If it's a small elevation, like a few metres, then the change in Patm will be so small that it is insignificant and the pressure at the bottom of the tank will effectively be unchanged. If you take it to the top of Mt. Everest vs sea level you will have a significt difference. Check what the value of Patm is that you've been given and go with that. It's just common to assume Patm = 101kPa for simple problems like this
Good
Thanks
what if the height of the oil was not given? what shall i do? should i use Pgh?
I these problems, you will only be given a maximum of one unknown, so just rearrange for the missing value
@@Engineer4Free thanks a lot