Presentation on theme: "Unit 3: Fluids and Dynamics. Pressure Differences: Fluids naturally flow from an area of high concentration to an area of low concentration The movement."— Presentation transcript:
Unit 3: Fluids and Dynamics
Pressure Differences: Fluids naturally flow from an area of high concentration to an area of low concentration The movement of fluids from an area of higher pressure to an area of lower pressure occurs in both natural and constructed systems
Atmospheric Pressure: Every layer of air exerts pressure on layers below. Gravity is pulling the air particles down. Air pressure changes with altitude Higher altitude = air is less dense (less compression) Lower altitude = air is more dense (more compression)
Fluid Pressure: The pressure of all fluids (gas, liquid) increases with depth Pressure at sea level = kPa = 1 atm (atmosphere) Every 10m in depth = 1 atm
Buoyancy: The tendency for objects to rise or float in a fluid Occurs because of differences in density of the object and fluid Buoyant Force: upward force exerted by a fluid Convection: the process of heat transfer through the flow of a heated substance such as air or water
Reading Check Answers p Your eardrum is a very thin membrane that can move in response to a difference in air pressure. If the difference in pressure on either side of the eardrum becomes great, you experience a “pop” inside your ear as the pressure equalizes. 2. Air pressure pushes the drink up the straw and into your mouth. 3. The straw makes such a tight seal that as you draw the juice up the straw and reduce the air pressure inside the juice box, the box buckles inward. The air pressure outside the juice box pushes the walls of the box together.
Reading Check Answers p kPa, or one atmosphere (1 atm) 5. Water is pumped into the submarine to control buoyancy. When water enters, the submarine’s weight increases, making it more likely to sink. 6. The object sinks.
Check Your understanding p (a) The purpose of the pumping is to build up pressure inside the bottle. 1. (b) The pressure inside the bottle becomes greater than the pressure outside. This results in fluid being forced from the area of high pressure in the bottle to the area of low pressure outside the bottle. 2. Fluid sprays out farther from the bottom hole because the pressure is greater at the bottom of the barrel than at the top. 3. As Tara blows into the balloon, the pressure builds inside the balloon. The pressure increases to the point where the force outward from the pressure in the balloon is greater than the force Tara’s lungs are able to produce.
Check Your understanding p The air pressure at high altitude is low; so low, people cannot get enough oxygen particles into their lungs to survive. For this reason airplane cabins are kept at a much higher pressure than the low- pressure atmosphere they are flying through. If a door on the airplane were to open, air would move out of the airplane from high to low pressure. 5. (a) The illustration should show equally sized arrows up and down, indicative of the forces of buoyancy and gravity. 5. (b) Yes, it is possible, as long as the buoyant force is equal to the gravitational force.
Check Your understanding p (a) The diagram should indicate high pressure inside the mattress, and low outside the mattress. Particles in the mattress should be shown closer together, as they are being forced together by Sascha’s weight. 6. (b) The diagram should indicate equal pressure inside and outside the air mattress. Particles both inside and outside the mattress should have the same distances between particles. This is because the pressure inside and outside the mattress is the same. 6. (c) The diagram should indicate high pressure inside the mattress, and low outside the mattress. Particles in the mattress should be shown closer together, as they are being forced together by Sascha’s weight. This is what is responsible for the movement of air out of the air mattress.
Fluid Mechanics Fluid System: a system that makes use of a gas or liquid to perform tasks Pascal’s Principle: Force that is applied at one point is transmitted to another point using an incompressible fluid Static Pressure: the force exerted by an enclosed, non-moving fluid when pressure is applied to the fluid Dynamic /Velocity Pressure: the force exerted by a fluid in motion
Hydraulics Hydraulics: the study of how liquids act when they are under pressure Hydraulic Systems: a device that uses liquid under pressure to apply force in order to move something How it works Applied Force to enclosed liquid creates Pressure moves liquid (along pipes, tubes, hose) causes Motion at other end 7AC2EA621B670EA182397AC2EA621B670EA1823&first=0&adlt=strict 7AC2EA621B670EA182397AC2EA621B670EA1823&first=0&adlt=strict
Hydraulic Fluid Transportation Valve: a device for controlling the passage of fluid through a pipe Pumps: are used to give the force that pushes the liquid. Pumps put the liquid under pressure Liquid must be under pressure to move against the force of gravity A liquid under pressure can travel long distances There are many types of pumps an dthey all work to create areas of low and high pressure to move a liquid along a pipe.
Reading Check p Liquid. 2. When pressure is applied to a liquid that is continuous and enclosed in a pipe or tube, the force is transmitted along the liquid. 3. A pump can be used to raise or move fluids. A pump creates areas of low and high pressure to move fluid. 4. Fluids can be controlled and directed by opening and closing valves.
Pneumatics Pneumatics: the use of gas in an enclosed system under pressure Pneumatic Systems: a system in which an enclosed gas transmits a force causing motion A pneumatic system uses a compressor (since gas can be compressed) Compressor: a device that that compresses air to build pressure When pressure is released (air particles spread apart quickly) it exerts a strong, steady force that can perform powerful tasks
Problems with the systems Hydraulic /Pneumatic systems require pressure to work Therefore a crack/hole will let fluid leak = reduced pressure = reduced work Also a blockage will let fluid leak = reduced pressure = reduced work
Reading Check p Hydraulic multiplication can be used to multiply the force exerted by a liquid. 2. Challenges include reaching remote locations with pipes, avoiding leaks, minimizing resistance in pipes by avoiding twists and turns, and avoiding blockages. 3. A hydraulic system uses liquid; a pneumatic system uses gas. 4. A vacuum cleaner has a motor that spins a fan at high speed. The fan creates an area of low pressure inside the vacuum cleaner, and the higher-pressure air from the room rushes into the vacuum.
Check Your Understanding Answers p.333 #1 - 6, 8
Check Your Understanding Answers: 1. Sharp turns create resistance to flow; this reduces the efficiency of the movement of fluid in the pipeline. 2. Buildup of material inside the pipeline can reduce fluid flow. Also, leaks must be found and repaired to prevent loss of fluid. 3. (a) The sprayer is dynamic in the sense that the fluid spraying out is moving. It is static in the sense that the enclosed fluid on the inside of the sprayer is being squeezed, and is capable of applying a force even though it is not moving. 3. (b) The higher pressure on the inside of the tank pushes the liquid out toward the area of lower pressure outside the sprayer.
Check Your Understanding Answers: 4. This is accomplished with a pump; pumps can move fluids up against gravity. 5. The diagram should show two pistons of different size connected to each other by a contained liquid. Applying force to the smaller piston will result in the force being multiplied at the larger piston. 6. The vacuum creates an area of low pressure inside it with a rapidly moving fan. The higher-pressure air in the room moves toward the area of low pressure, through the vacuum cleaner hose. The cardboard is held on to the hose due to the high pressure of the room forcing it against the hose. If you want to remove it, you must apply enough force to overcome the force caused by the air pressure in the room. 8. The spray will be equal from both holes because pressure is distributed equally throughout a contained fluid.
Many natural systems are based on fluids and pressures They can be found in the atmosphere (hurricanes), inside the earth (volcanoes), in the oceans (whirlpools), and inside the human body. Fluid Systems in Humans Humans rely on fluids and fluid systems Water, and water balance, is vital for life Humans are affected by air pressures (breathing and fluid pressures (the circulatory and respiratory systems)
The Circulatory System (Hydraulic System) The circulatory system transports blood through the body Heart is the pump Blood Vessels are the pipes Blood is the fluid under pressure Heart beats increase & decrease pressure Blood leaves heart under High pressure Blood pressure refers to how hard blood pushes against the walls of your body's blood vessels
Disorders of Blood Circulation Like in all hydraulic systems, deposits (clogs) or cracks inside of pipes decreases the hydraulic system's effectiveness. Fatty deposits build up in arteries to slow blood flow Smoking and obesity also increase blood pressure High BP = too much force on pipes (burst) Low BP = not enough blood flow (blocked)
Reading Check Answers, p Like pipelines, blood vessels transport fluid from place to place under pressure. 2. If you fill a balloon with water and then push on it, the pressure moves through the water in all directions. When the heart contracts, it places pressure on the blood in much the same manner. 3. The first number is a measure of the pressure caused when blood is pushed out of the heart. The second number is a measure of the pressure that occurs as the heart relaxes and refills with blood. 4. Clogged arteries, smoking 5. Weak heart, low water levels in blood
The Respiratory System (Pneumatic system) Inhaling expands the rib cage, increasing volume (by making a bigger space) and decreasing pressure (in the lung) Air from outside, which has oxygen in it, is at a higher pressure so it enters the low pressure in the lungs Exhaling is the diaphragm and rib muscles pushing inwards, decreasing volume (by making smaller space) and increasing pressure (in the lung) Air is pushed out of lungs/body
Disorders of Breathing Breathing is affected by narrowed passageways, especially swelling from infections and allergies Smoke, polluted air, coal dust and asbestos are also harmful Asthma is a respiratory disease that narrows the passageways for air entering and leaving the lungs. Asthma can be triggered by smoke and pollutants, exercise, stress and dust An inhaler is used to deliver tiny droplets of medicine to passage ways
Reading Check Answers, p When you inhale: expansion of the chest cavity creates an area of low pressure in the lungs. 2. When you exhale: contraction of the chest cavity creates an area of high pressure in the lungs. 3. The diaphragm moves up and down to help contract and expand the chest cavity. 4. Bacterial or viral infections, asthma 5. Asthma attacks cause the pathway to the lungs to narrow, making it difficult to breathe.
Check Your Understanding: p.343 #1 – 3, 5 - 7
Check Your Understanding Answers 1. A hydraulic system moves fluid under pressure. This is what the human circulatory system does. 2. Pneumatics is the use of gas (usually air) in an enclosed system under pressure. This is what the human respiratory system does. 3. The diaphragm moves down when you inhale, enlarging the chest cavity and creating an area of low pressure in the lungs. This causes the higher pressure air from the surroundings to rush into the lungs.
Check Your Understanding Answers 5. The CPR compression of the chest is a way to mimic the action of the heart. When the chest is compressed, the heart is compressed, forcing blood out of it to the rest of the body. This is not as good as the natural action of the heart, but may help to keep a person alive until medical personnel can restart the heart. 6. The heart pumps blood under pressure to all areas of the body. When you stand up too quickly, the blood pressure momentarily drops in the head area, interrupting the supply of blood to the brain. It takes a few moments for the body to adjust and normalize blood pressure. In the meantime, you will feel a bit dizzy.
Check Your Understanding Answers 7. (a) The diaphragm jerking upward causes the chest cavity to get smaller very fast, which compresses the air in the lungs, raising the air pressure. 7. (b) When a hiccup occurs, the rapid compression of the chest cavity causes air to be rapidly forced out of the lungs (this causes the hiccup sound).
Chapter Review: p. 344 #1 – 4, , 13
CHAPTER REVIEW ANSWERS 1. The diagrams should indicate that the air in the container can be compressed, while the water cannot. 2. When a balloon is filled, air is forced into it under pressure. The walls of the balloon contain the area of high pressure in the balloon. When the wall of the balloon is popped, the high-pressure air inside the balloon moves rapidly outward.
CHAPTER REVIEW ANSWERS 3. The diagram should show that pressure increases with depth. 4. (a) Hydraulics uses liquid, while pneumatics uses gases (usually air) under pressure. Pneumatics requires the use of a compressor. Hydraulics usually uses pipes, pumps, and valves. 4. (b) Both terms describe systems that operate while under pressure to move fluids from one place to another.
CHAPTER REVIEW ANSWERS 7. Water must often be moved great distances to areas that are at higher elevations. Moving the water against the force of gravity requires a pump. 8. All of the following reduce fluid flow: twists and turns in the pipe, build-up of material inside the pipe such as sludge or rust, pipes that are too narrow, and leaks.
CHAPTER REVIEW ANSWERS 9. Initially the heating of the tank caused the particles inside the tank to move farther apart, which caused some of the particles to leave the tank. When the tank was sealed and cooled, the remaining particles moved closer together, causing an area of low pressure. The high pressure of the surroundings pushed against the tank toward the low-pressure area, crushing the tank. 10. Air flows from areas of high pressure to areas of low pressure, causing winds.
CHAPTER REVIEW ANSWERS 13. (a) When the pump handle is forced downward, it pushes the air particles trapped in the pump together, compressing the air. 13. (b) The inflation needle is a very tiny tube, which offers much more resistance to the flow of air.
Summary: Fluids Under Pressure ..
Particles will move from an area of high pressure to an area of low pressure. Pressure in a liquid will increase with depth.
Summary: Buoyancy Buoyancy is the tendency of objects in fluids to rise or sink due to density differences with the surroundings. Buoyant force is the upward force exerted by a fluid; if it is less than the force of gravity, the object will sink. If buoyant force is greater than gravity, the object will rise.
Summary: Hydraulics Fluids in motion have dynamic pressure that can exert force to complete tasks. Hydraulics is the study of pressure in liquids. Hydraulic systems create pressure that moves through a contained liquid. Pumps force liquid to create pressure in a hydraulic system. Valves control flow in hydraulic systems. Hydraulic multiplication takes advantage of an incompressible fluid to transmit and increase force from one point to another. Pneumatics is the use of compressed air in an enclosed system. Blockages will interfere with the flow of fluid in a hydraulic or pneumatic system.
Summary: Fluids in Natural Systems Humans rely on fluid systems for proper body function. Proper water levels in the body must be maintained. Blood pressure is the force of blood on the walls of blood vessels. The human respiratory system uses changes in air pressure for breathing. Air pressure changes are caused by changes in chest volume.
Summary: Disorders of Natural Fluid Systems High or low blood pressure can result in health problems. Clogged blood vessels can reduce blood flow, increase blood pressure, and have a negative effect on human health. Clogged or swollen air passageways can interfere with breathing. Asthma is a disease of the respiratory system that interferes with the normal flow of air into the lungs.