L esson 21
Pipewor k
“Oh man, not again,” James muttered and Elijah turned his head from the quiet muttering of the television set, listening to his cousin banging around in the kitchen.
“Hey man, what on earth are you doing?” Elijah’s words sounded heavy to his own ears with sleep and the jetlag of the day. He and James had been up all that evening working on the
papers for his admission to the school downtown, about a ten minute drive from the house. The
paperwork had been nearly completed when Elijah had heard a drip from the kitchen and alerted
his cousin. The paperwork mostly finished, lying on the coffee table next to a stack of textbooks
and a few empty mugs with the honey pooled in the bottom, the rest of the little house was quiet
until James started knocking around in the kitchen, attempting to find and fix the leak.
“All this inviscid flow, just pooling underneath the sink and being wasted,” James called, and Elijah jerked his head up, gray eyes darting around and hearing the clank of a toolbox
rattling like a skeleton in the kitchen as James dug around for a wrench.
“I guess you’re waiting for me to ask what on earth an inviscid flow is,” Elijah called back, and James chuckled as was his habit, clanking the wrench on what Elijah guessed might be
the pipes underneath the sink, probably stored away in some cabinet.
“It’s the flow of an ideal liquid, so called in the study of fluid dynamics. Fluid dynamics isn’t all that rosy, mind you, but it has to do with physics so I was made to study it. There was this Swiss scientist named Daniel Bernoulli who published a book about fluid dynamics. His
stated Bernoulli’s principle stated that in order for an inviscid flow to occur, there should be an increase in the speed of the fluid that correlates with a decrease in the pressure, or a decrease in
the fluid’s potential energy. His principle is actually really the offspring of the concept about conserving energy, which is that when you have a steady, easy flow of something, adding all the
forms of mechanical energy in a fluid along a streamline will get you the exact same sum as
points along the streamline. This dictates that the sum of kinetic and potential energy has to be
constant. So if there’s an increase in the speed of fluid, like if you turn up the speed of water gushing into your bathtub, at the same time there’s an increase in dynamic pressure and kinetic energy there has to be a decrease in static energy and potential energy. I mean, it makes sense. If
you cause water to squirt out your pipes, obviously the potential energy is kinetic energy.”
“I though conservation was saving energy. Squirting water and junk is like wasting energy, right?”
James’s footsteps came into the living room, and Elijah could imagine him adjusting his glasses and leaning in at the corner. “Well I mean, in laymen terms, the law about the
conservation of energy states that energy cannot be created or destroyed, it can only change
forms, as in potential energy turning into kinetic energy after being acted upon. So when you add
up the energies in a given system, or action, it creates a constant. And without friction to stop a
movement, such as a pendulum set to swinging, it would just keep going on and on.” 173 “Like that weird doohickey with the silver balls on the string and if you push them, like
one ball hits on another and they just keep on swinging and stuff, until you stop them.” “Exactly like that, that’s pretty much what the balls on string set out to demonstrate. And then relating all that to fluid mechanics once more, fluid particles are subject to pressure and
their weight, only those two factors. So if fluid is flowing along a horizontal streamline, when
the speed of fluid increases, it’s because it’s moving from an area of high pressure to an area of low pressure, and the same runs for a decreasing speed. Guess where the highest speed
happens?”
“Like…I guess when the pressure is the lowest?”
“Right. Say, you don’t go to school or anything, do you?”
“Um, no, since someone won’t finish my papers,” Elijah grumped, and James snickered and walked back into the kitchen.
“Back to applying some pressure on my poor sink pipes…man I wished I’d paid more attention when my dad was trying to show me all of this housework stuff, I didn’t know I’d even be working on sinks by myself. I was going to live with my parents until I retired and moved to
the south of France.”
“Wow, that’s pretty unlikely,” Elijah called into the kitchen, and the silence that settled was friendly and as comfortable as James had ever felt it be between them. He continued
tightening the pipes underneath his sink and listening to the television burble in the background.
Ever since the two of them had sat on the couch together and Elijah had spoken in as bare an
honesty as James had ever heard him, they had crept closer and closer to functioning as a tiny
family unit. James had lived alone for years, teaching and coming home to tea and research and,
from time to time, an interesting documentary on the science or history channels. He could only
hope that the progress made the other day was not of the temporal kind, that they could regress
and go back to awkward silences, angry words thrown out even if they were truth. The blowup
Wednesday night seemed to be all but forgotten in both of their minds but James felt he had a lot
to learn about acting, talking, presenting himself as a brother, cousin, or even a father figure. It
had been merely his parents and him for his entire life, before he had moved out and began
teaching and living on his own. He did not want to hit another standstill as he did the previous
week, if he could just ensure somehow that Elijah wasn’t going to blow up at the slightest provocation, or that James himself could be honest and did not walk on eggshells around him—
His thoughts were interrupted as Elijah’s cane came sliding into the kitchen. “Hey, so you go to church like every Sunday morning, right?”
James stopped what he was doing and looked in his direction, knowing that Elijah could
tell from where noises came and whether someone was looking at him, a gut feeling that James
was quickly learning to respond to. “Yes, every Sunday that I can unless I’m like iced in or something…”
“Well if I’m going to live here or whatever, I may as well go out and do stuff. I kinda liked grocery shopping the other day and I don’t just want to sit around even when I’m like in school and stuff…so like if you want to take me to church and stuff I guess I can’t stop you.”
174 “You want to come to church with me?” James asked, very softly, carefully.
Elijah shrugged and attempted to appear nonchalant. “Sure.”
“This Sunday?”
“…sure. Why not.” 175 L esson 21 Part 1
W hat is inviscid flow?
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W hat is fluid dynamics?
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Explain Bernoulli’s principle. __________________________________________________________
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Looking H igher: What sorts of things can you study with the aid of an understanding of fluid
dynamics?
176 L esson 21 Part 2
Today you will conduct an experiment that demonstrates Bernoulli’s principle. You will need an electric hair dryer, one with a circular nozzle, a normal-sized balloon, and a
table tennis ball or some other small ball.
Blow up the balloon and tie it off. Let go of the balloon and observe how it travels. Does it stay
stationary, or drop, or rise?
Turn on the hair dryer, holding it in one hand and pointing the nozzle towards the ceiling. Place
the balloon directly over the stream of air. What happens to the movement of the balloon? If you
tilt the nozzle to one side, does the balloon move in any way? Try moving the hair dryer around
and demonstrate at what point the hair dryer’s stream of air affects how the balloon moves. Now place the table tennis ball in the stream of air from the hair dryer nozzle. How does it
move? Try moving the nozzle around and observe how it affects the movement of the tennis ball.
How does density affect this experiment? How does the movement of the nozzle affect the
movement of the hair dryer and table tennis ball?
177 L esson 21
W hat is the law of conservation? How does it relate to
entropy in the universe?
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How might the law of conservation be an argument against the Big Bang theory?
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W hat is pressure?
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W hat is dynamic pressure, static pressure, and the difference between these two?
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178 __________________________________________________________
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Looking H igher: How does the law of conservation relate to the Bernoulli principle?
179 L esson 21
This week for your essay, research the Swiss scientist Daniel Bernoulli. In what subset of
physics did he specialize? What led him to develop his ideas? What sorts of experiments did he
conduct? Did he use simple mechanisms to help develop his ideas? Include a photograph of his
scientist with your essay.
180 L esson 21
During your observation time this week, look in the
heavens to find evidence for a creator. This may sound like
a generic assignment but think practically about what you
have been looking at. What about the solar system evinces
a creator? Can you find symmetry in the heavens? Discuss
this concept with your family. What conclusions can you
draw? How do the heavens evince a creator?
In addition to this, find the constellations and bright stars you have been finding, as well as any
visible planets, looking back over your drawings to determine how the heavens might have been
perceived to have moved.
Use the space below to draw what you observe in the night sky, which stars are visible, and the
orientation of the moon, if visible. You may also use the lines to write about this.
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