THE BIG MOVERS – HYDRAULICS
Most machines that move very large objects use a hydraulic system.
System that uses a liquid under pressure to move loads.
- works according to Pascal’s Law.
Before hydraulic systems most construction was done by hand
Ex) Pyramids, castles, great wall of china
Remember : Pneumatic systems use gases while hydraulic systems use liquids!
PRESSURE IN FLUIDS
Measure of the amount of force applied to a given area.
Pressure (Pa) = Force (N)/Area (m²)
Pressure applied to an enclosed fluid is transmitted equally in all directions through out the fluid.
*this means fluids do not become compressed, unlike gases.
A PISTON CREATES PRESSURE
Hydraulic systems work because of pistons.
A disk that fits tightly inside a cylinder.
- As the disk moves it either pushes fluid out or draws a fluid in
- Size can vary
Hydraulic system is a combination of 2 pistons attached by a flexible pipe.
Small Piston Pressure = Large Piston Pressure
So... We can say that:
Force of the Small Piston / Area of the small piston = Force of the Large Piston / Area of the large piston
Re-written we express it as such:
F (small)/A (small) = F (large)/A (large)
Used to apply force to the fluid.
Transfers the force to the load
PRESSURE EXERTED EQUALLY IN THE FLUID PROVIDES THE MECHANICAL ADVANTAGE.
Mechanical Advantage (MA) = Output Force/Input Force
EVALUATING MECHANICAL DEVICES
Evaluate a mechanical device based on the following criteria:
- Consider the environment it is being used in
- Consider if it has potential for development
Evaluate 2 different mechanical devices using the criteria given.
A non-government association that tests and approves a wide range of products to ensure they are safe for use by the consumer. CSA stands for Canadian Standards Association.
Technological advances and mechanical devices
Technology and devices have come a long way since the invention of simple machines. Advances in technology can have broad implications on human society:
- Changes in society
- Changes in the environment
- Changes in production capacity
- Changes in human behaviour
Watch the following video and write down all the different changes in society, human behaviour, environment, and production capacity.