As larger communities developed, newer more complicated machines developed.
New larger energy sources like coal, oil, and electricity combined with new technologies, caused an industrial revolution.
This led to an increase in people’s standard of living.
But has also led to people now being dependent on technology.
COMPLEX MACHINES
COMPLEX MACHINES: A system in which simple machines all work together.
SYSTEM: A group of parts that work together to perform a function. Ex. Bicycle (which simple machines does a bicycle employ)
SUBSYSTEM: A smaller group of parts in a complex machine with one function. (Ex) Car - braking and steering
NAME ALL THE SUBSYSTEMS OF A BIKE!THINK OF A HOUSEHOLD ITEM THAT IS A COMPLEX MACHINE!
SUBSYSTEMS THAT TRANSFER FORCES
LINKAGE:Abelt or chain to transfer energy from a energy source to an object.
(Ex) bicycle chain
TRANSMISSION: A special type of linkage for transferring energy from the engine to the wheel in large vehicles such as cars or trucks.
more useful when larger loads must be moved.
Also known as a gearbox, or gear train
GEARS: A pair of wheels with teeth that interlink; when they rotate together, one gearwheel transfers turning motion and force to the other.
gear wheels work together in gear trains (2 or more gears).
gears can change the speed, force, and direction of motion
gears will alternate the direction of spin, if a driving gear spin clockwise the adjacent driven gear will spin counterclockwise
gears integrate with other gears , while gears that integrate with a linkage (ex. gears on a bike) are called sprockets
DRIVING GEAR: Gear that has original force applied to it. (Can also be called the ‘driver gear’) DRIVEN GEAR: Gear that receives the force after.
HOW DO GEARS AFFECT SPEED? MULTIPLYING GEARS: When driving gear is larger than the driven gear = The turning speed in the system increases.
The larger driving gear will make one rotation while the smaller driven gear will make many rotations
REDUCING GEARS: When the driving gear is smaller than the driven gear = The turning speed in the system decreases.
The smaller driving gear will make many rotation while the larger driven gear will make one rotation
MECHANICAL ADVANTAGE
Machines Make Work Easier. - A winding road is actually a series of inclined planes with switchbacks, which allow cars to drive up a steep hill.
MECHANICAL ADVANTAGE :Amount by which a machine can multiply a force. Also called the Force Ratio. INPUT FORCE:Force applied to the machine. OUTPUT FORCE: Force the machine applies to the object.
FORCE IS MEASURED IN NEWTONS (N).
Mechanical Advantage (MA) = Force Output (N) / Force Input (N)
EX 1 To pull a weed out of a garden, you can apply a force of 50 N to the shovel. The shovel applies a force of 600 N to the weed. What is the mechanical advantage of the shovel?
EX 2 To pry open a soda can lid, you can apply a force of 50 N to a car key. The car key applies a force of 390 N to the lid. What is the mechanical advantage of the car key?
EX 3 To pry a wooden board off of a treehouse, you can apply a force of 50 N to a lever. The lever applies a force of 750 N to the board. What is the mechanical advantage of the lever?
A MECHANICAL ADVANTAGE LESS THAN 1 Useful for tasks that do not require a large output force. Or for increasing speed. (Ex) Bicycle – the output force is used for speed. (Ex) Larger gear driving a smaller gear
EXAMPLE ANSWER KEY Example 1 - Mechanical Advantage of 12 Example 2 - Mechanical Advantage of 7.8 Example 3 - Mechanical Advantage of 15
SPEED RATIO
SPEED: Measures the distance an object travels in a given amount of time. Speed = Distance (m)/ Time (s)
SPEED RATIO:Measure of how the speed of the object is affected by a machine. Speed ratio describes how much faster the user is moving than the load is working. Speed Ratio (SR) = Input Distance (m)/ Output Distance (m)
EX 1A gear mechanism of two gear is in motion. The driving gear moves a total of 3m, while the driven gear moves a total of 12m. What is the speed ratio of this mechanism?
EX 2A pulley system is pulled a distance of 10 m, this moves a box that is attached to the pulley 1.5m. What is the speed ratio of the pulley system? ** A machine can increase or change the direction of the force that you apply. But, the cost is that the force the user applies must move farther than the load.
EXAMPLE ANSWER KEY Example 1 - Speed Ratio of 4 Example 2 - Speed Ratio of 6.67