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Otago HSFY chat - archive
- Thread starter jeavey
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Ok im also having trouble with b of this question. There was a bit of writing before the question stem that pretty much said you can treat the blood as a newtonian fluid and that the effects of viscosity can be ignored.
A large artery has a diameter of 7 mm and carries blood
which flows with a peak velocity of 0.15 m s−1 . This
vessel eventually feeds a network of capillaries which to-
gether have an area approximately 400 times that of the
large artery which feeds into them. In this model, the
capillaries are identical to each other and have a diameter
of 7.5 µm.
(a) Suppose that the diastolic blood pressure is 130 mmHg
at the level of the heart and the blood velocity in the large
artery at the heart is 0.15 m s−1 . What is the blood ve-
locity in the artery at a point 1 m below the heart? (The
density of blood is 1050 kg m−3).
[answer=0.15]
(b) If the artery is severed at a a point 1 m blow the
heart, what is the maximum velocity of blood flow from
the artery?
[Answer=7.28m/s]
A large artery has a diameter of 7 mm and carries blood
which flows with a peak velocity of 0.15 m s−1 . This
vessel eventually feeds a network of capillaries which to-
gether have an area approximately 400 times that of the
large artery which feeds into them. In this model, the
capillaries are identical to each other and have a diameter
of 7.5 µm.
(a) Suppose that the diastolic blood pressure is 130 mmHg
at the level of the heart and the blood velocity in the large
artery at the heart is 0.15 m s−1 . What is the blood ve-
locity in the artery at a point 1 m below the heart? (The
density of blood is 1050 kg m−3).
[answer=0.15]
(b) If the artery is severed at a a point 1 m blow the
heart, what is the maximum velocity of blood flow from
the artery?
[Answer=7.28m/s]
Wow what a random question haha. They'd never give you something like that, especially not with mmHg to work with. It's worded pretty badly too. For part b I have to mash some numbers randomly in my calculator before getting the answer.
Let's call point 1 as being at the level of the hear and point 2 as being 1m below the heart, and use Bernoulli's equation:
P1 = 118.6kPa absolute pressure
1/2p(v1)^2 = 1/2 x 1050 x 0.15^2
pgh1 = 1050 x 10 x 0 (take the level of the heart as the reference point for the surface, so if you're at the same level, then the depth h is 0)
P2 = 101.3kPa (atmospheric pressure, because it's been cut so is exposed)
1/2p(v2)^2 = 1/2 x 1050 x (v2)^2
pgh2 = 1050 x 10 x 1 (1m below reference level)
Putting these values into the equation and solving for v2 gives 7.28ms^-1. When you are doing P1-P2, you can just use +17.3kPa as P1-P2 instead of having to subtract the absolute pressures from each other.
Study sheets? You mean cheat sheets? Everyones was pretty different but it was the same A4 side both sides. Mine would be completely useless to most people lol. It had some random equations on it and a diagram.
Let's call point 1 as being at the level of the hear and point 2 as being 1m below the heart, and use Bernoulli's equation:
P1 = 118.6kPa absolute pressure
1/2p(v1)^2 = 1/2 x 1050 x 0.15^2
pgh1 = 1050 x 10 x 0 (take the level of the heart as the reference point for the surface, so if you're at the same level, then the depth h is 0)
P2 = 101.3kPa (atmospheric pressure, because it's been cut so is exposed)
1/2p(v2)^2 = 1/2 x 1050 x (v2)^2
pgh2 = 1050 x 10 x 1 (1m below reference level)
Putting these values into the equation and solving for v2 gives 7.28ms^-1. When you are doing P1-P2, you can just use +17.3kPa as P1-P2 instead of having to subtract the absolute pressures from each other.
Study sheets? You mean cheat sheets? Everyones was pretty different but it was the same A4 side both sides. Mine would be completely useless to most people lol. It had some random equations on it and a diagram.
Last edited:
Sorry to burst your bubble but that's not true. Well done on hubs!
Lol pete I think you should be thanking skyglow for helping you with physics, not me 
But I'll accept adoration for doing absolutely nothing 
SASOL: doesn't just have to be a BSc, you can do whatever degree you like. And yes, you can apply under rural if you meet the conditions.
But I'll accept adoration for doing absolutely nothing SASOL: doesn't just have to be a BSc, you can do whatever degree you like. And yes, you can apply under rural if you meet the conditions.
D
Deleted member 4350
Guest
23/25. I got the axial skeleton question and pennate muscle questions wrong. *sigh* lol...how did everyone in your colleges do? When do the CELS results come out. omg physics on wed!! *gulp* :-|
D
Deleted member 4350
Guest
They repeated a few questions, some questions were **** easy, others not so much. I found it quite difficult overall
SASOL
Regular Member
I thought physics was hardish.......I freaked out at the first few questions, but came back later and realised I could do them. Pretty sure I got all the calculations, and the statement questions I went bad in, purely because I didnt read the question properly. So I think I got at least 4 wrong, which is annoying. Yay for plussage!!
nottellingu
Regular Member
Most ppl in HSFY can apply to aussie unis without them knowing ur non standards ay...sneakyyy (n)
But aren't NZ'ers classed as internationals so it costs a lot more to go to an Aussie uni?
Really? Lol and I also heard that because Aus unis use a GPA system out of 7 and we use one out of 9, if you get 7+ on the NZ scale then you get 7/7 GPA when you apply to Aus unis haha.
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