Fluid Mechanics

How do Fluids work? We're going to need to learn about fluid mechanics. Fluid mechanics explains how the air moves around your car, how food colouring moves through the water, And it explains what makes quicksand act like quicksand.

While a car is moving, it's going to interact with the fluid that it's moving through which will be air in most cases. As the car interacts with the air, the two can affect one another, and this can lead to what we call transfer. The transfer is when something moves or is moved, from one place to another. There can be a transfer of momentum or a transfer of heat maybe even mass. But if we're looking at moving fluids, then we'll often have transfer of momentum, which can be better understood with Fluid Mechanics. Fluid Mechanics studies how fluids respond to the forces exerted on them.

So how exactly do fluids move and how does a particle or anything for that move within a fluid? To answer these questions, we need to know about stress, strain, and viscosity. Suppose we have fluid between two flat plates. If we were to move the bottom plate, what would happen to the fluid? How would it move? At the top and bottom, where the fluid is in contact with the surface, the individual particles of the fluid will go through something called the no-slip condition. In the no-slip condition, fluid in motion will come to a complete at a solid surface and assume a zero velocity relative to the surface. The particles of the fluid that are touching the solid will stick to its surface, meaning that they won't slip. Because of this, the fluid particles in contact with the bottom plate will move with it, while the fluid particles at the top will stay with the stationary plate.

This is happening due to stress, the force that's applied to a cross-sectional area of an object or substance. If the forces are normal or perpendicular to the surface of the object, then we have normal stress. If it's parallel, then we have shear stress. We can find stress by taking the applied force and dividing it by our cross-sectional area. Once the fluid is stressed, the degree to which it stretches is called strain. The strain is the deformation that stress causes on a system. If the deformation causes something in a system to become either shorter or longer, Then we can find its strain by taking the change in length and dividing it by the initial length. And this is called normal strain. But if the deformation is a change in angle between two segments that had been perpendicular to each other, then we have shear strain. And we can find that by subtracting the change in angle from the original angle, which will either be pi over 2 or 90 degrees, depending on your units. So all of this is what would happen if our bottom plate was moving. But what if neither plate move, and we have a pump driving the flow of the fluid between them?

The no-slip condition would apply. While the fluid moved, its particles at the surface of the two plates would stay stationary. But we need to take into account is viscosity. Viscosity is essentially a measure of a fluid's resistance to flow, and it's often referred to as the thickness of a fluid. Water has a low viscosity and honey has a higher viscosity. The law of viscosity says that Newtonian fluid as fluids with a viscosity that's independent of stress. No matter how much stress you put on the fluids, its viscosity never changes. Non-Newtonian fluids, don't follow the law of viscosity like quicksand and water mix with cornstarch. This means that their strain can change too. If you add stress to quicksand it will thin out and you will sink and if you mix water with cornstarch and add stress it will thicken. Most of the non-Newtonian fluid will thin out. Like how quicksand sucks you in, you step on the surface of quicksand creating stress and making quicksand become less viscous.


Now, there's still the matter of how one fluid moves within another fluid. In 1868, Osborne Reynolds graduates college, he becomes the first professor of engineering at Owens College in Manchester. Reynolds did an experiment on moving water he found when you add a drop of food colouring which has the same density of water. When he adds a drop of food colouring into slow-moving water the flow of the food colouring maintained its place and pattern in the centre of the water we call this Laminar flow. Laminar flow is the flow of fluid when each particle of the fluid follows a smooth path, paths which never interfere with one another.

But when he adds a drop of food colouring into fast-moving water the food colouring spread out and diffused mixing with the water we call this Turbulent flow. Turbulent flow is the fluid motion characterized by chaotic changes in pressure and flow velocity. Those are the main two types of flow that Reynolds found but we also have something called transitional flow. Transitional flow is a mixture of laminar and turbulent flow, with turbulent in the centre of the pipe and laminar flow near the edges. To find out if the fluid is flowing laminar or turbulent we need to use Reynolds number for the flow of a fluid in a pipe by taking the diameter of the pipe and multiplying it by the velocity of the fluid and the density of the fluid, then dividing all of that by the viscosity of the fluid. The value we get for our Reynold number will be dimensionless, meaning there are no units attached to it, but it can tell us a lot about the movement of a fluid. Reynolds number help us how predictable or how chaotic fluid flow will be.

This is because we look at Reynold number as a ratio of inertial force to viscous force. Inertial force means to represent the driving kinetic movement of the fluid, which results in chaotic flow movement, like the swirling motion of eddies and vortices. Viscous force means represent resistance to flow and are move likely to provide slow, steady motion. A low Reynold number represents laminar flow and a high Reynold number represents a turbulent flow. Laminar flow usually has a Reynold number lower than 2100 and turbulent flow usually have a Reynold number high than 4000. Reynold number between these two values typically represents the transitional flow. 

Why is fluid mechanics is important because we need to know-how fluid workaround us and object and how fluid move from one place to another like sewage. Sewage is important because we make a lot of waste and we need to get rid of it this is why fluid mechanics. Also, fluid mechanics help us to develop a better car and others. 

Oral Presentations - Reflection

1. What was your presentation about? My presentation is about how to make people more open to you by being open yourself.

2. Which part of your work are you proud of? being open and sharing how people can be more open.

3. Were there any challenges? Speaking to the class.

4. Would you do anything differently next time? Speaking more clearly.

Ancient Egyptian Inventions - Papyrus

Papyrus is a plant which once grew in abundance, primarily in the wilds of the Egyptian Delta but also elsewhere in the Nile River Valley, but is now quite rare. Papyrus buds opened from a horizontal root growing in shallow freshwater and the deeply saturated Delta mud. These plants once were simply part of the natural vegetation of the region, but once people found a utilitarian purpose for them, they were cultivated and managed in farms, harvested heavily, and their supply depleted. Papyrus still exists in Egypt today but in greatly reduced number.  

Illustrate Knowledge Of Stone Age Art

 This stone-age art is made from black paint and sand. The idea came from Chauvet in France. The animal is a bull. I chose the bull because I got the idea of bull of heaven in the story when Gilgamesh kill the bull of heaven. The bull is like a god or a magic animal. I think that the bull symbolize masculinity, power, and the violence from the gods. 

Social Studies - Tech and Change

In Social Studies, we have been looking at screen time. How long we were on our technology. To do this we use an app that you can use to see how much screen time the class have in a day, week, etc. The charts show how long we been on our technology and the type of technology.





























In Social Studies, we also learn the history of cellphones. This timeline explains it.

How do fish make electricity

Fish using electricity is more common than you think. Underwater, where light is scarce, electrical signals offer ways to communicate, navigate, and find plus, in rare cases stun prey. Nearly 350 species of fish have specialized anatomical structures that generate and detect electrical signals. These fish are divided into two groups, depending on how much electricity they produce. Scientists call the first group the weakly electric fish. Structures near their tails called electric organs, produce up to a volt of electricity, about two-thirds as much as a AA battery.

 How do this work? The fish's brain sends a signal through its nervous system to the electric organs, which is filled with stacks of hundreds or thousands of disc-shaped cells called electrocytes. Normally, electrocytes pump-out sodium and potassium ions to maintain a positive charge outside and negative charge inside. But when the nerve signal arrives at the electrocytes, it prompts the ions gate to open. Positively charged ions flow back in. Now, one face of the electrocytes are negatively charged outside and positively charged inside. But the far side has the opposite charge pattern. These alternating charges can drive a current, turning the electrocyte into a biological battery. The key to these fish's powers is that nerve signals are coordinated to arrive at each cell at exactly the same time. That makes the stacks of electrolytes act like thousands of batteries in series. The tiny charges from each one add up to an electrical field that can travel several meters. Cells called electroreceptors buried in the skin allow to fish to constantly sense this field and the changes to it caused by the surroundings or other fish.

 The peter's elephant nose fish, for example, has an elongated chin called a Schnauzenorgan that's riddled in electroreceptors. That allows it to intercept signals from other fish, judge distances, detect the shape and size of nearby objects, and even determine whether a buried insect is dead or alive. But the elephant nose and other weakly electric fish don't produce enough electricity to attack their prey. That ability belongs to the strongly electric fish, of which there are only a handful of species.

The most powerful strongly electric fish is the electric knife fish, more commonly known as the electric eel. Three electric organs span almost its entire two-meter body. Like the weakly electric fish, the electric eel uses its signals to navigate and communicate, but it reserves its strongest electric discharges for hunting using a two-phased attack that susses out and then incapacitates its prey. First, it emits two or three strong pulses, as much as 600 volts. These stimulate the prey's muscles, sending it into spasms and generating waves that reveal its hiding place. Then, a volley of fast, high voltage discharges causes even more intense muscle contractions. The electric eel can also curl up so that the electric fields generated at each end of the electric organ overlap. The electrical storm eventually exhausts and immobilizes the prey and the electric eel can swallow it's meal alive. The other two strongly electric fish are the electric catfish, which can unleash 350 volts with an electric organ that occupies most of its torso, and the electric ray, with kidney-shaped electric organs on either side of its head that produce as much as 220 volts. There is one mystery in the world of electric fish is why don't they electrocute themselves? It may be that the size of strongly electric fish allows them to withstand their own shocks, or that the current passes out of their bodies too quickly. Some scientists think that special proteins may shield the electric organs, but the truth is, this is one mystery science still hasn't illuminated.

Persuasive Essay

Persuasive Essay Why should bring back extinct animals

It is easy to imagine life with the Passenger pigeon, woolly mammoth and etc roaming
around. They all have one thing in common, they’re extinct. In fact, scientists estimate
that 5 billion species have come and gone off this planet. But what if we could bring them
back? What if extinction didn’t have to be a permanent thing? Right now scientists are
using revolutionary new genetic techniques to try to bring back some of these species. 

The woolly mammoth is an impressive specimen. It was the king of the tundra for
millions of years. Then it rather suspiciously disappeared around the same time that
humans appeared. Most scientists think it’s likely that they were hunted to extinction.
Most of the species that have gone extinct in recent years are because we destroyed the
habitat, we’ve introduced species, or we’ve killed them outright, like the passenger
pigeons. It was hard to imagine, at the time, that this bird species that are so abundant
could actually be hunted to extinction. But we managed to do that. While it’s normal for
species to die out over time because of evolution or a cataclysmic event some scientists
think the earth is now entering a new age of mass extinction, called the Anthropocene or
Holocene extinction, caused by human. Animals, plants and insects are dying out at a
rate of 1000 to 10000 time faster than ever before, with dozens of species going extinct
every single day. Some scientists estimate that as many as 30 to 50 per cents of
all species could be headed towards extinction by end of the century. But what if
extinction didn't have to be a thing? What if we could bring species back at will? 

How do we do it? Woolly mammoth, Passenger pigeon, dodo, and etc are extinct but
these species DNA is still around, in places like museum drawers and buried in the
ground. Today, scientists think de-extinction might be the answer to saving our plant’s
lost biodiversity.