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5:10 AM
@JohnRennie hi
I need ur help in a simple question
how the trees are so tall?
 
@JackRod Hi :-)
 
I mean I was observing a tree which was roughly 115m
 
Do you mean how do they have the mechanical strength to stay upright?
 
no,to survive they need water right at stem of the the top?
for water to travel 115 m from ground is looking totally unreasonable
 
Ah, you mean how do they suck water up higher than 30m i.e. one atmosphere?
 
5:13 AM
yes excatly
 
I did some calculation and some physical experiment
and maximum height I got is 10m from a very thin tube
obviously more thinner the tube more the hight
 
Yes, because in simple column taller than 10m the pressure difference exceeds 1 atm at the top and the water the top would boil and turn to water vapour.
 
yes
 
But in trees water transport involves osmosis and it isn't just a simple column of water. In effect cells pump water between them.
 
5:18 AM
but can U give what should be pressure difference between ground and top(115m)?
if assume ground to be at 1 atm
 
The pressure difference in the tree is not the same as the pressure difference would be ina column of water.
That's because the cells of the tree have mechanical strength and hence they can exert an upward force on the water.
Suppose you had a chain of buckets 1m apart and extending up to an arbitrary height. To pump water up you only need a pressure equal to 1m height i.e. just enough to get to the next bucket.
 
ah
do there exist a chance of air bubble inside the tube of the tree
 
I don't know to be honest. I suspect the bubble would dissolve i.e. the gas inside would go into solution in the fluids around it.
 
my friend says it does not convert water into vapour
because of activation energy
9 mins ago, by John Rennie
Yes, because in simple column taller than 10m the pressure difference exceeds 1 atm at the top and the water the top would boil and turn to water vapour.
 
I don't know enough about this subject to be able to talk about with any confidence.
 
5:26 AM
cool thanks sir
 
I would have guessed that inside a tree there were lots of things that could act as nuclei for bubble formation so I doubt bubble nucleation would be a barrier.
 
one more question I have
 
Yes ... ?
 
related to mechanical tv
I forgot the name of the scientist who discover the mechanical tv
sir how to they convert a image into beam of electrons
 
John Logie Baird FRSE (; 13 August 1888 – 14 June 1946) was a Scottish inventor, electrical engineer, and innovator who demonstrated the world's first live working television system on 26 January 1926. He went on to invent the first publicly demonstrated colour television system, and the first viable purely electronic colour television picture tube.In 1928 the Baird Television Development Company achieved the first transatlantic television transmission. Baird's early technological successes and his role in the practical introduction of broadcast television for home entertainment have earned him...
 
5:30 AM
I did read the pendulum experiment to duplicate an image but how they used a mechanical tv two show a real-time image on tv
 
Baird's TV did use an electron beam. The "mechanical" bit was just how the image was scanned.
 
sir I cannot imagine how they convert an image into the beam of electron how this beam of electron form exactly the same image
 
I don't know how Baird's TV worked.
You could probably Google it.
 
:)
 
Aha, this is how the image was scanned:
A Nipkow disk (sometimes Anglicized as Nipkov disk; patented in 1884), also known as scanning disk, is a mechanical, rotating, geometrically operating image scanning device, patented in 1885 by Paul Gottlieb Nipkow. This scanning disk was a fundamental component in mechanical television, and thus the first televisions, through the 1920s and 1930s. == Operation == The device is a mechanically spinning disk of any suitable material (metal, plastic, cardboard, etc.), with a series of equally-distanced circular holes of equal diameter drilled in it. The holes may also be square for greater precision...
 
5:54 AM
yes
 
I think the idea is that a lens produces an image on the disk, then as the disk rotates it measures the brightness by letting through only a small part of the image to a detector behind the disk.
 

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