Mechanical Systems

Topic 4: Force, Pressure, and Area

Vocabulary Words Area Pressure Pascal’s law Hydraulic lift Closed system

Topic 4: Force, Pressure, and Area P=F/A Force is measured in Newton's (N) Area is measured in square metres (m2) Pressure is measured in Pascals (Pa) 1000 Pa = 1 kPa

Pressure Review A bronze statue weighs 2400Newtons and has a base that is 4 meters by ½ meter. What is the pressure the statue exerts on the floor? How many N are required to create 150Pa of pressure on 5m2?

Pascal’s Law Pressure exerted on a contained fluid is transmitted undiminished in all directions throughout the fluid and perpendicular to the walls in the container. http://www.youtube.com/watch?v=iD55ynlUH8g

Topic 5: Vocabulary Terms Hydraulic systems Pneumatic systems Valve Pumps

Hydraulic Lift A mechanical system that raises heavy objects, such as vehicles at a service station. It uses a fluid under pressure in a closed system. (closed- system is a self-contained collection of parts) http://www.edumedia-sciences.com/en/media/442-hydraulic-lift

Hydraulics and Pneumatics Hydraulics: use the force of a liquid in a confined space, such as an oil pipeline. Hydraulics apply apply two essential characteristics of fluids- their incompressibility and their ability to transmit pressure. Howstuffworks "A Hydraulic System“

Hydraulics at Work Backhoe Bulldozer Cherry picker

Hydraulics and Pneumatics Pneumatic systems do not seal gas-usually air- in a mechanical system in the same way that hydraulic systems seal in hydraulic fluid. Air passes through the pneumatic device under high pressure and then escapes out the device. High pressure air may come from a machine that draws in outside air and compresses it.

Pneumatics at Work Jackhammer Pneumatic nailers Sandblasters http://www.edumedia-sciences.com/en/media/381-steam-locomotive

Hydraulics and Pneumatics in Your Body Your body’s respiratory system is more complex than any pneumatic machinery. This system is made of lungs; tubes that allow air to enter and leave the lungs; and muscles that cause your lungs to expand and contract.

Valves and Pumps Valve: used to control the fluid A valve is a movable part that controls the flow of fluid by opening and closing Valves can be made to operate automatically using the pressure that the valve is controlling Many pumps use automatic valves controlled by pressure to move fluids in a specific direction The valve is pushed open by pressure on one side and will close if the pressure becomes greater on the other side of the valve

https://www.youtube.com/watch?v=ruM4Xxh x32U How does your heart pump blood?

Topic 6: Combining Systems When a simple machine is part of large system we call it a subsystem It is often hard to see all the subsystems in a large machine. How many simple machines can you see under the hood?

Disk Brakes: The brake pedal subsystem is a Class 2 lever Disk Brakes: The brake pedal subsystem is a Class 2 lever. The pressure of the driver’s foot on a brake pedal is transmitted by fluid pressure to the wheels of the car.

Backhoe: The three levers are the boom, the dipper and the bucket.

Transmission http://www.edumedia- sciences.com/en/media/831-motion-transmission- systems

Think About IT!

Topic 7 – Evolution of Machines There are many machines and reasons for the changes in machines and objects we use every day What are some reasons for the changes in the design for an object? Example – the telephone

History of the Bicycle http://www.edumedia- sciences.com/en/media/341-bicycle-history We know the designs of bicycles have changed over the years – why have the designs changed?

Opening a Can Look at the picture on the next slide. What are some advantages and disadvantages in each of the designs?

Evolution of Transportation Changes in Transportation https://www.youtube.com/watch?v=FaLCQo8NJFA Why did we change our methods of transportation? Was there a major time in history where we made the most change? http://www.edumedia-sciences.com/en/media/825- history-of-transportation

Evolution of Moving Water https://www.youtube.com/watch?v=X1-FMc8tIgs Stop at 6 minutes. How did Early Civilizations get their water? Was there a method that would be easiest?

Evaluating a Machine When we evaluate a machine, we must look at the design and function as well as the social and environmental impacts. Are there machines that we could improve? Name one, and discuss why it should improve, considering the 4 main points for evaluation.

Unit Project Making Mousetrap Catapults or Cars!

You’re finished Science 8