Ch 7 and Ch 8 that is hard
Chapter 7 Technological systems pages 196-223
7.1 Characteristics of a system
System: it’s a group of parts, mechanisms, devises or machines that are assembled to perform a specific task. Ex: Train is a technological system. It’s designed to transport people from one place to another; however, the train is made up of smaller systems: the control cab, the cars, the brakes, etc.
General diagram of a system
1. OVERALL FUNCTION OF THE SYSTEM
- It’s what the system needs to do
- Ex: overall function of heating system is to heat. Function of telephone is to all people to have conversations
2. CONTROLS
- Controls manage or change what happens in a system.
a. Mechanical (like gear shifters on bike that change bike speed)
b. Electric or electronic (like keys on a keyboard or buttons on a remote)
c. Optical (like automatic openers on some doors)
3. INPUTS
- Any elements that enter a system and help it function. 7 categories
a. People: workers, suppliers
b. Equipment: saws, trolleys, trucks
c. Information: knowledge, instructions
d. Energy: muscle power, electricity
e. Materials: wooden boards, fabrics, nails
f. Capital: money, buildings, land
g. Time: production time, management time
4. PROCESSES
- Series of actions that a system must do to its inputs to fulfill its role.
5. OUTPUTS
- Anything that exits a system after it has finished working.
- Some outputs are:
a. Desirable: results (when you start a car and press gas pedal, motion is the desired output)
b. Not desirable: waste (a car produces exhaust fumes and dirty oil)
Useless info: Leonardo da Vinci interested in bats and birds’ flights. Studied the structure and mechanisms of wings, placement of feathers, etc. He created flight devices (parachute, hand glider)
7.2 components of a system
The components of a system are the different elements (like parts, mechanisms, devices or machines) that make up a system.
Example a car system has subsystems (electrical system, suspension system, braking system, engine system) then each of the subsystems can be turned into parts.
7.3 Manufacturing process sheet
Outlines the process and steps to follow for making an object. Describes all the steps, it lists the equipment, materials, and time required for each step.
A manufacturing process sheet is an essential document for mass-producing a technical object.
The header contains general information about the part being made.
Each section describes a general step that is then broken down into specific steps.
The section names are the following:
1. Measuring and marking
Before creating a technical object, the materials need to be measured carefully and cut lines need to be marked. Measure each part, mark lines, materials
2. Machining and forming
During this step parts are cut using tools (machines) or are folded to give them the needed shape (forming)
3. Finishing
Remeasure parts, Sanding parts, painting parts,
4. Assembling
Last step in fabrication process. Assemble parts of object, use appropriate links, consider the materials and assembly type (glue, nails, screws, bolts), choosing guiding controls, follow assembling instructions
5. Disassembling
You make have to disassemble an object for transport, or to store in smaller places. Disassemble section by section, place parts of each section in separate bags, or containers, write info on bag or container
7.4 Energy transformations
Energy: is the capacity to produce a change. It describes an object’s ability to produce movement, release heat or emit rays (like light, for example).
Useful form of energy: is a form of energy that humans can use to meet their needs.
Forms of useful energy
1. Mechanical energy.
Comes from the motion of an object or its position in space. Ex: a fan. Rotating blades move air quickly.
2. Thermal energy
Comes from the agitation of particles in matter. Usually produced from combustion (of wood, gasoline, gas etc.) ex: thermal energy cooks food in an oven, heats air in a heater, heats water in a water heater.
3. Luminous energy
Is carried by light. Many sources of light, most involve some sort of transformation of energy. Ex: electrical energy is transformed into luminous energy in maps, signs, etc.
4. Electrical energy
It’s the energy associated with the movement of electricity. Can be produced from most energy sources. It can also be transformed into many other forms of energy. Electricity can be carried over long distances.
Humans mainly us the 4 forms of energy. Many different natural energy sources can be transformed into one or more forms of useful energy.
What is a motor?
A motor is a system that can use energy from electricity, a combustible or a battery to do a job like heating, rotating, pushing, pulling. It short it transforms energy into thermal or mechanical energy. In a vehicle, the motor uses chemical energy from gasoline to rotate the wheels.
How do batteries work?
It’s a container that stores 2 chemical substances. One contains + terminal and one – terminal. When the 2 terminals are linked to electrodes the chemical substances react and produce electricity. The chemical energy in batteries is transformed into electrical energy.
Energy transformation: is the conversion of one form of energy into another.
Examples of energy transformation from natural sources.
1. Solar energy: photovoltaic solar panels are used to transform solar energy into electricity (calculator). Thermal solar panels can also be used to convert solar energy into heat (the tiles and pipes on our roof to heat water in pool).
2. Wind Energy: is mostly used to produce electrical energy through wind turbines. This is not a direct transformation. The wind produces mechanical energy that rotates the blades of the turbine, then an alternator converts the mechanical energy into electrical energy.
Wind energy Mechanical energy Electrical energy
3. Hydraulic energy: many techniques for turning hydraulic energy, which comes from the motion of water, into other forms of energy. Ex: a hydroelectric power plant
Hydraulic energy Mechanical energy Electrical energy
4. Biomass: they could be wood and peat. They act as combustibles. Burning biomass produces thermal energy, which then can be used directly or transformed into electricity.
5. Fossil Energy: comes from oil, coal, and natural gas. Is transformed into thermal energy through combustion. Ex: a gas engine transforms fossil energy into thermal energy than mechanical energy. Ex: Thermal power plant.
Fossil energy thermal energy Mechanical energy Electrical energy
6. Nuclear energy: used to produce energy in nuclear power plants.
Nuclear energy Thermal energy Mechanical energy Electrical energy
In Quebec we mostly use hydraulic energy to produce electricity.
Chapter 8 Engineering Green Book Pg 224-243
Definition
Engineering: Involves everything needed to study, design and create technological projects used to solve problems and make life easier, faster or safer.
8.1: Simple Machine
- A simple machine is a tool that allows a task to be completed faster or with less effort.
- A simple machine is a device with few pieces. It allows mechanical energy to be used more efficiently or comfortably by reducing the force or time needed to perform a task.
The simple machine doesn’t change the amount of energy needed to perform the task; they just distribute the energy over a larger distance or a longer period of time. Simple machines reduce the force by increasing distance or changing direction, not by doing less work.
SIMPLE MACHINES:
1. Inclined plane: sloped surface; less force, more distance
2. Wedge: two inclined planes; splits or separates objects
3. Lever: rigid bar that pivots around a fulcrum
4. Wheel and axle: reduces force or increases distance
5. Pulley: grooved wheel and rope
8.1.2 Inclined Plane
Mountain roads are winding. And the are often steep.
An inclined plane is a flat surface that is set at an angle to a horizontal surface. Think of a ramp off the back of a truck.
inclined planes reduce the amount of effort (force) needed to raise or lower a load by increasing the distance traveled.
WEDGES
Wedges and screws are both similar to inclined planes.
Wedges, which are two back-to-back inclined planes, reduce the amount of force needed to split or separate two objects. An axe is a type of wedge.
Screws
A screw reduces the force needed because it converts turning motion into linear motion. Spreading the force over a longer distance.
An endless screw is sometimes called a worm is used in snowblowers. It is when the screw is held in one place, it cannot turn. Instead, the material around it moves. Archimedes developed this instrument during a trip to Egypt.
8.1.3 What is a LEVER?
= a seesaw is a type of lever. It makes lifting another person very easy.
Definition: A lever is a simple machine made up of a rigid bar that pivots around a fulcrum (the center or point that something turns around)
3 parts of a lever:
- The effort force (the force exerted on the lever) E
- The fulcrum (the pivot point of the lever) F
- The resistance force (in this case, it is defined as the weight of the load being lifted) R
A lever changes the amount of effort needed to lift something. Levers can be used in different mechanisms, like wheelbarrows and shears.
3 types of levers
Lever types depend on the location of the fulcrum relative to the where the resistance and effort is.
1- First-class lever
In this type of lever, the fulcrum is located between the 2 forces. When the fulcrum is in the middle. Ex: Scissors, seesaws and current clamps
Advantages: this lever always moves in the opposite direction of the force being applied.
It can change the direction of the force. When you push down in one end, the other end moves up.
It can multiply force (it can lift a heavy object with less effort)
Increase speed and distance of movement
2- Second-class lever
Here the resistance is located between the fulcrum and the effort. Resistance is in the middle.
Example: Nutcrackers, wheel barrows, and bottle openers.
Advantages: This type of lever puts distance between the effort and the resistance. It distributes the weight of the load over a larger distance, allowing more force to be applied. Also called “power lever”
3- Third class lever
The effort is located between the resistance and the fulcrum. The effort is located in the middle. Ex: tweezers, hockey sticks and fishing rods.
Advantages: This lever reduces the force applied to the load. Its useful becausse it can increase speed and precision when moving a load. Called also a “speed lever”
To know:
Reverse direction of force = FIRST CLASS LEVER ex: seesaw, scissors.
Reduce force = SECOND CLASS LEVER ex: wheelbarrow
Increase force AND distance = THIRD CLASS LEVER ex: broom, hockey stick
Parts of a Lever
F = Fulcrum → pivot point (hinge or axle)
E = Effort → where you push or pull
R = Resistance → load being moved
Lever Classes
First-Class Lever:
Fulcrum in the middle
Pattern: E – F – R
Purpose: Changes direction of force
Examples: Scissors, pliers, seesaw
Second-Class Lever:
Resistance in the middle
Pattern: F – R – E
Purpose: Reduces force needed
Examples: Wheelbarrow, bottle opener
Third-Class Lever:
Effort in the middle
Pattern: F – E – R
Purpose: Increases speed and distance (not force)
Examples: Hockey stick, tweezers, broom, arm
Test Sentence: “This is a ___-class lever because the ___ is in the middle.”
Levers in the human body.
Raising our heads use a FIRST-CLASS lever.
- The neck muscles exert the EFFORT
- The joint near the ear is the FULCRUM
- The head is the LOAD
Standing on our tiptoes is a SECOND-CLASS lever
- the toe joints = the FULCRUM
- the body weight is the LOAD
- the EFFORT is exerted by the muscles in the calves which pull calves upward.
Biceps act as THIRD-CLASS lever when they are contracted (lifting weights)
- the hand and wrist are the LOAD
- the EFFORT is exerted by the muscle attached to the radius (a bone in the forearm)
- the elbow joint is the FULCRUM
8.1.4. what is a WHEEL
Wheels invented around 3500 BC. Made transportation much faster.
A wheel and axle (rod) make up a simple machine. It reduces the force needed to move an object. A wheel can increase the distance an object moves.
When a wheel rotates, so does the axle. A wheel is always attached to an axle.
PULLEYS
Def: a pulley is a simple machine made of a wheel with a groove and a rope. Examples: crane, blinds, hoists.
A pulley can:
- change the direction of a force (pull down to lift up)
- reduce the force needed when several pulleys are used together.
1 pulley = changes direction of motion ex: blinds
Lots of pulleys together = reduces the force needed to lift a load.
8.2. MOTION TRANSMISSION SYSTEMS
Motion Transmission System: it’s a mechanism that transmits motion from one part to another without modifying it. It can perform a rectilinear translation, a rotation or a helical motion.
4 types of motion transmission systems.
1. FRICTION GEARS
v Transmits rotational motion through simple rubbing contact (also called friction between wheels)
v Smooth wheels pressed together
v Can slip if pressure is low
v Example: generator contains a small wheel that presses against the wheel of the bicycle. When bike moves forward, it turns generator wheel allowing device to produce energy.
2. GEAR TRAIN
v Made up of small toothed wheels (gears) that transmit rotational motion.
v Used to increase or decrease the speed of a motion inside a technical object.
v Speed of the rotation depends on the size of the gears and the number of teeth that each gear has.
v Can change speed, force and direction Example watch, clock.
3. PULLEYS AND BELT
v Device made up of 2 or more pulleys (friction gears) and a belt
v Motion transmitted by friction
v Can slip if force is too high
v Example: car engine
4. CHAIN AND SPROCKET WHEELS
v Toothed wheels (sprocket wheel) connected by a chain
v Motion is transmitted by the teeth in the wheels that fit into the loops of the chain (rotational motion)
v No slipping
v Handles large forces
v Needs lubrication
v Example: bicycle
Motion transmission systems are made of wheels, belts and chains.
8.3 MOTION TRANSFORMATION SYSTEMS
Different then transmission systems because it doesn’t transmit motion it modifies the motion.
Def: this type of system turns one type of motion into another. Most of the time theses systems transform a rotational motion into a translation motion or vice versa.
3 types of motion transformation systems
1- Rack and pinion
v Made with a toothed wheel (called a pinion) and a straight toothed rod (called a rack)
v When pinion is rotated, it moves the rack because teeth of two parts fit in together.
v Works other way too. Meaning the rack can move and it will rotate the pinion.
v Rotational motion to translational motion Ex: posts of tennis nets
2- Cam and follower
v Transforms a rotational motion into a bidirectional translational motion
v A cam is a part that is oval shaped or that rotates off center
v The rod (called a follower) presses on the cam.
v When cam turns and the “bump” meets the follower it creates a back-and-forth motion Ex: Valves of a car engine
3- Connecting rod and crank
v The crank is the part that rotates
v Connecting rod is a bar or stem attached to the crank
v This system usually connected to a piston that performs translational motion
v The rotational motion of the crank is therefore turned into the translational motion of the piston. Motion transformation can happen in reverse
v Very fast motion
v Has to be lubricated. Ex: wheels of train
Key difference:
Transmission system = same motion
Transformational system = different motion