I couldn't understand the concept of water having a lower boiling point at higher altitude but need to be heated longer for it to get boiled. Isn't it faster to boil it when boiling point decreases? I'm soo confused. Also, thank you for this hard work, I am actually bad at Physics since high school, so my foundation is bad. I couldn't understand fluid mechanics with my own teacher's presentation but since you are showing real life examples and explaining every single thing without thinking "they must know it already" it's sooo much easier and entertaining for me to understand. It also shows that you love to teach. Thank you so much. I appreciate it a lot.
Thanks for the really nice comments! To answer your question. As you said, water boils at a lower temperature at high altitude because of the lower pressure. You are correct: It will take LESS heat input to boil, and will boil FASTER. I was talking about say, cooking noodles in water that's boiling at 80C rather than 100C. It makes sense that the cooking time will have to be longer to soften/cook the noodles. There are cookbooks to help make this adjustment, if you live in a high altitude city. Hope that helps. Thanks again!
@@FluidMatters The water at a lower pressure will boil sooner, once it starts however which cup will empty sooner? Will the lower pressure cup empty sooner than the higher pressure with the same rate of heat added when the both have the same mass?
@@FluidMatters This can be broken down into two parts. How much time it takes to start boiling, and how much water boils per second after boiling starts. Are they both faster? Is this not a legitimate question for a scientific mind to ask? Should I just assume the answer is yes?
If you look at a saturated steam table you will see that h_fg is a weak function of pressure. That's not a path to understanding vapor pressure in my opinion.
Why would you have to boil the noodles for longer if the water boils at 70 C instead of 100 C. Thinking about it intuitively, you'd reckon that your typical college dinner would be ready much faster no?
Take this idea to the limit....Liquid water can boil at 0C, given a low enough pressure. At 0C, the noodles wouldn't cook at all, even though the water was bubbling. In fact, it can be a food safety issue when cooking meat. See: www.fsis.usda.gov/shared/PDF/High_Altitude_Cooking_and_Food_Safety.pdf
I couldn't understand the concept of water having a lower boiling point at higher altitude but need to be heated longer for it to get boiled. Isn't it faster to boil it when boiling point decreases? I'm soo confused. Also, thank you for this hard work, I am actually bad at Physics since high school, so my foundation is bad. I couldn't understand fluid mechanics with my own teacher's presentation but since you are showing real life examples and explaining every single thing without thinking "they must know it already" it's sooo much easier and entertaining for me to understand. It also shows that you love to teach. Thank you so much. I appreciate it a lot.
Thanks for the really nice comments! To answer your question. As you said, water boils at a lower temperature at high altitude because of the lower pressure. You are correct: It will take LESS heat input to boil, and will boil FASTER. I was talking about say, cooking noodles in water that's boiling at 80C rather than 100C. It makes sense that the cooking time will have to be longer to soften/cook the noodles. There are cookbooks to help make this adjustment, if you live in a high altitude city. Hope that helps. Thanks again!
@@FluidMatters Thank you for answering (:
@@FluidMatters The water at a lower pressure will boil sooner, once it starts however which cup will empty sooner? Will the lower pressure cup empty sooner than the higher pressure with the same rate of heat added when the both have the same mass?
@@brentlackey8316 Enough already...
@@FluidMatters This can be broken down into two parts. How much time it takes to start boiling, and how much water boils per second after boiling starts. Are they both faster? Is this not a legitimate question for a scientific mind to ask? Should I just assume the answer is yes?
Very useful to understand the cavitation phenomenon and vapour pressure.
Glad it was helpful!
All the videos for this introductory Fluid Mechanics course are available at: www.drdavidnaylor.net/
how can we prevent cavitation? could u pls give some recommendations pls
Great work from contents to presentation
Thanks for the kind words.
Great explanation! thank you very much
At 7:20 did you mean that the condensate is about a thousand times *more* dense than vapour?
Yes.
Great explanation
Cool video!
Does the latent heat of evaporation change with pressure?
If you look at a saturated steam table you will see that h_fg is a weak function of pressure. That's not a path to understanding vapor pressure in my opinion.
Useful contents 😊
Why would you have to boil the noodles for longer if the water boils at 70 C instead of 100 C. Thinking about it intuitively, you'd reckon that your typical college dinner would be ready much faster no?
Take this idea to the limit....Liquid water can boil at 0C, given a low enough pressure. At 0C, the noodles wouldn't cook at all, even though the water was bubbling. In fact, it can be a food safety issue when cooking meat. See: www.fsis.usda.gov/shared/PDF/High_Altitude_Cooking_and_Food_Safety.pdf
Hello Profesor, I would like to be your PostDoc researcher. Please give me your email to contact with you. Thanks.
Sorry, I don't have any positions open. My lab is shutdown for the foreseeable future.
Sir your voice please
?