Water Pressure and Hydraulic Systems

1. Water Pressure and Hydraulic Systems Presentation Created by Mr. Liu and Nobody Else! (not trying to take full credit or anything)

2. Hydraulic Systems • The Balloon Bulger uses the incompressibility of water to cause motion. The force that you apply on the bottle is transmitted through the liquid to make the water particles move. When the water particles move into the balloon, they make the flexible walls of the balloon move. • Hydraulics is the study of pressure in liquids. Devices transmit applied forces through a liquid to move something else, because of pressure, are called hydraulic systems. In most hydraulic systems, a force is exerted on a continuous, enclosed liquid.

3. Hydraulic Systems • This applied force creates pressure that moves the liquid through a series of tubes, pipes, or hoses, which causes a motion at the other end of the system. The Balloon Bulger is a simple model of hydraulic system. It behaves like the lifting mechanism that moves a barber’s or dentist’s chair, for example.

4. Hydraulics in Action • Rescue workers use hydraulic-powered devices to cut away or move heavy metal at the scene of automobile accidents. One such device is called the Jaws of Life. A powerful pump is used to move the hydraulic fluid continuously through the hoses to produce a strong force in each attached rescue tool. The three types of tools that can be attached to the Jaws of Life are shown directly below. The spreaders can be used to pry open a door, for example. However, their spread is limited. When an opening is made large enough, a ram can be fitted into the space to spread the opening even farter apart. Rams come in different sizes, depending on how large an opening is needed. The cutters act like huge pruning shears and can cut through thick and other materials.

6. Hydraulics to Transport Fluids • Just as water gushes out of an open faucet, liquids under pressure flow away from the applied force in all directions. Hydraulic systems can be used to transport fluids over large distances. The ancient Romans constructed huge aqueducts to transport water from lakes to distant cities. Today, water, natural gas, and oil are typical examples of fluids transported in extensive pipelines. Pumps provide the force that pushes the fluid through the pipes.

7. Hydraulics to Transport Fluids • Think about the water that comes out of your faucet. Where did this water come from? Drinking water can come from lakes, rivers, and underground wells deep in Earth’s crust. Unless you live underground, water must flow up in order to get from its source to most people’s homes. How does water travel up to reach homes in highrise apartment buildings? To travel so high, water must be placed under pressure in order to give the water particles the energy to move against gravity. Otherwise, the water would simply rest in puddles in the lowest parts of the pipe! The amount of pressure transmitted in the pipes must be enough to transport the liquid over a large distance, but not too much to make the pipes burst.

8. Hydraulics to Transport Fluids • Friction in the pipes – caused by rough surfaces or numerous bends in the pipeline – can affect fluid pressure. The particle theory suggests that particles lose energy as they brush past each other in confined spaces and as they bump into the walls of the pipeline. Therefore, pumping stations are frequently needed to restore the pressure lost on long routes. The water reaching your home has probably been to a nearby pumping station to maintain a constant water supply to your home.

9. Hydraulics to Transport Fluids • In most hydraulic transport systems, it is important that the fluid keeps travelling away from the pump. Some pumps cannot do this on their own. Valves are devices used to regulate the flow of a liquid in hydraulic systems. One-way valves ensure that the fluid can flow in one direction but not in the opposite direction.

10. Body Hydraulics • One of the most efficient hydraulic transport mechanisms is the human circulatory system. In humans, blood must be kept under pressure so it can reach all parts of the body. The highest blood pressure occurs close to the heart. Blood pressure at more distant regions, such as the hands and feet, is much lower. The constant beating of the heart, which is the pump, keeps the blood moving throughout the arteries and capillaries, which are like pipelines. Valves in the veins keep the blood moving in one direction.

11. Body Hydraulics • Blood pressure increases and decreases between heartbeats. Immediately after the heart contracts, a surge of blood causes high pressure in the arteries. Then, before the next heartbeat, the pressure falls, only to increase again at the next contraction. Blood pressure is measured with a sphygmomanometer, more commonly referred to as a blood pressure cuff. Both the maximum pressure, called systole, and the minimum pressure, called diastole, are measured using this device. A normal blood pressure reading is 120/70. This means that the systolic pressure is 120 mm Hg (millimetres of mercury), and the diastolic pressure is 70 mm Hg (millimetres of mercury).

12. Homework Questions • In which direction is pressure exerted in a fluid at rest? (1 mark) • Pipelines are used to transport liquids such as natural gas. Why are these pipelines made with few bends and kept free of dirt and rust? (2 marks) • What are the names of the two blood pressure readings? What does each reading indicate? (4 marks) • Doctors always remove all the air from a needle before inserting the tip of the needle into a patient’s blood vessel. Why do you think an air bubble in the bloodstream would be dangerous? (3 marks)