You know all about the motion of individual objects. Now, let's talk about how to analyze the motion of a fluid.
Log in J Burkhard 8 years agoPosted 8 years ago. Direct link to J Burkhard's post “In the paragraph titled, ...” In the paragraph titled, "What is the equation of continuity?" it says that the volume in must equal the volume out. I am a physics novice/dunce so I really need this spelled out for me. It has a "for instance" that I am struggling with. I am hoping it is a mistake, but honestly with my physics knowledge I can't be sure. "For instance, if in one hour you pump 2 meters cubed of water into a pipe that is already full of water, 3 meters cubed has to flow out of that pipe during that same hour. " Is this correct? I am trying to understand why the two numbers wouldn't be the same...Please let me know if I am missing something! Thanks! • (15 votes) Benjamin Torr 8 years agoPosted 8 years ago. Direct link to Benjamin Torr's post “Hi JYou are correct in ...” Hi J You are correct in thinking this is a typo. The volume flowing in and out of the pipe are the same so the statement should read, "if in one hour you pump 2 meters cubed of water into a pipe that is already full of water, 2 meters cubed has to flow out of that pipe during that same hour." (25 votes) Fomentia 9 years agoPosted 9 years ago. Direct link to Fomentia's post “"People often mix up the ...” "People often mix up the ideas of volume V and speed v since they look so similar." Wait a second, I thought v stood for velocity, not speed! Am I mistaken, or is the text wrong? • (8 votes) mir.schwabe 9 years agoPosted 9 years ago. Direct link to mir.schwabe's post “You're correct, but in th...” You're correct, but in this case, velocity and speed are the same thing. Speed is a magnitude (in other words, a number representing distance over time) while velocity is a vector - a speed that has a direction. Since liquid through a pipe is flowing in one direction, the direction part doesn't matter. Sal probably used the word speed to make it easier to understand. (31 votes) nicholas.miklave 7 years agoPosted 7 years ago. Direct link to nicholas.miklave's post “In the previous video, Sa...” In the previous video, Sal mentioned that the flux or flow rate is denoted by R but here it is being used as Q. Are they still the same thing just being denoted with diferrent letters or are they actually different measurements? • (11 votes) Fiona T 3 years agoPosted 3 years ago. Direct link to Fiona T's post “From what I've seen, volu...” From what I've seen, volume flow rate is usually denoted by the symbol Q. R is used for resistance in electricity and the gas constant in chemistry (PV = nRT). (1 vote) Caresse Zhu 9 years agoPosted 9 years ago. Direct link to Caresse Zhu's post “In the Mountain Dew probl...” In the Mountain Dew problem, the soda is carried from downstairs to upstairs. Should we consider the pressure that is needed to pump the soda up? • (5 votes) davidsantopietro 9 years agoPosted 9 years ago. Direct link to davidsantopietro's post “If you only want to relat...” If you only want to relate the speeds and areas of the pipe, you don't need to consider the pressure. The continuity equation Av=Av has to be true for any incompressible fluid (since the volume flow must be constant) )even if the pressure and height changes. If you wanted to determine the pressure necessary to pump the Mountain Dew, you would need to use Bernoulli's equation as well as the equation of continuity. (9 votes) ADITYA ROY a year agoPosted a year ago. Direct link to ADITYA ROY's post “I am answering this quest...” I am answering this question in January of 2023, so I hope you know where I looked for the answer of this question. The reason why Q is used specifically to represent volume flow rate is rooted in the historical conventions of fluid mechanics. The letter Q is used as an abbreviation for the Latin word "discharge" which is the act of releasing fluid, specifically refers to the flow rate of a fluid. The use of Q for flow rate is convenient because it is a single letter, easy to write and recognize, and is less prone to mistakes than writing out "flow rate" every time it needs to be referenced. It's common in physics and engineering to use symbols, often letters of the alphabet, as shorthand for certain quantities and concepts to save time and space, especially in mathematical equations and in technical drawings. This can improve the readability of the work, making it more straightforward to interpret and understand the results. • (6 votes) ahmedsalih28 7 years agoPosted 7 years ago. Direct link to ahmedsalih28's post “When I open the water tap...” When I open the water tap. I physical increase the the area of the outlet (the tap). However, it seems volume flow rate increase when I open the tap more . The equation of the continuity predicts that I would have the same volume flow rate with different speed depends on the outlet area, clearly this is not the case, I could fill a container in shorter time if I open the tap to its maximum compare if I open it slightly. Where I'm not getting it right? • (3 votes) thevalveman 7 years agoPosted 7 years ago. Direct link to thevalveman's post “as per the continuity equ...” as per the continuity equation A1vi = A2v2 it says that the value of Avhas a constant value throughout the pipe. So, if the area, A of a section of pipe decreases, the speed, v of the liquid there must increase so that the product, Av remains the same. • (2 votes) ahmedsalih28 7 years agoPosted 7 years ago. Direct link to ahmedsalih28's post “I hope someone answer thi...” I hope someone answer this question. Nicholas: Sharma Furthermore, A1v1=A2V2 ---> volume flow rate at 1 = volume flow rate at 2 (2 votes) Iris Buschelman 9 years agoPosted 9 years ago. Direct link to Iris Buschelman's post “I thought Sal said in the...” I thought Sal said in the video that Flux was V/t? And that Flux was R? Are Vol Flow Rate and Flux the same thing? • (2 votes) river phoenix 9 years agoPosted 9 years ago. Direct link to river phoenix's post “at 9:20 in "volume flow r...” at (1 vote) Jack Morrison 7 years agoPosted 7 years ago. Direct link to Jack Morrison's post “Say you have a hole cut i...” Say you have a hole cut in a pipe and the liquid within was flowing straight down and exiting horizontally out of the hole. How do you measure the width of this flow that would occur from the hole? • (2 votes) Estefano Barioni 7 years agoPosted 7 years ago. Direct link to Estefano Barioni's post “If the fluid is incompres...” If the fluid is incompressible, the equation of continuity will still apply. The volume flow rate at the exit of the pipe plus the volume flow rate through the role would be equal to the volume flow rate at the entrance of the pipe: Qentrance = Qexit + Qhole. (1 vote) Murtaza Mushtaq 6 years agoPosted 6 years ago. Direct link to Murtaza Mushtaq's post “what about vertical flow ...” what about vertical flow ? • (2 votes) Avizini 6 years agoPosted 6 years ago. Direct link to Avizini's post “While deriving the equati...” While deriving the equation of continuity we cancel the two g's so no matter what the value of g is we will cancel it out. Yes, gravity will have its effect. We will have to do more work in moving that water column up, nothing else. (1 vote)Want to join the conversation?
So, if the area, AAA, of a section of pipe decreases, the speed, vvv, of the liquid there must increase so that the product, AvAvA, v, remains the same. This means that fluids speed up when they reach a narrow section of a pipe and slow down when they reach a wider section of a pipe. This matches everyday experience—think about what happens if you block a portion of the water hose with your thumb, effectively reducing its area, AAA. The water must come out with higher speed, v, to ensure the volume flow rate, Av remains the same. This is why narrow nozzles, which reduce the area (A), attached to water hoses cause a significant increase in the speed, v of the fluid at that point.
but i noticed that in my home tap , when i fully open the tap it fills the bucket quickly as compared to when i open it half,(reducing the opening area of tap). but as per law of continuity ,bucket should be filled within same time in both cases.
Can you elaborate more, I don't get how the tap can regulate the (volume flow rate) by reducing the area. This is clearly doesn't explain the equation of the continuity.
"Doesn't the Equation of Continuity have nothing to do with time. Because as per A1v1=A2v2, there is no time"
Equation of continuity has everything to do with time, v is speed, speed is meter per second.
This means, the amount of water passing in 1 sec is the same at both ends.
9:20
Gravity must have its effect?
