Systems and Subsystems

• A system is a group of parts working together to perform a task, such as a can opener.

Physical Systems

• Physical systems involve physical parts performing a function, like the solar system or an electrical system.
• Human-made physical systems (tools, appliances) help us accomplish tasks faster.

Social Systems

• Social systems involve groups of people or organisms working together and establishing relationships, like bee colonies or the health care system.

Subsystems

• Subsystems are smaller systems within a larger system that help it perform its task.
• A can opener has holding/cutting and turning subsystems.
• The Global Positioning System (GPS) includes space, control, and user subsystems.
  • The space subsystem involves 24 orbiting satellites.
  • The control subsystem includes U.S. Air Force monitoring stations.
  • The user subsystem is a receiver.

Mechanisms

• Subsystems contain mechanisms that change forces, energy, motion, or actions.
• A force is a push or pull that can change an object's motion or shape.

Industries

• Industries are complex combinations of systems which produce needed goods and services
• They combine physical and social systems.

System Inputs and Outputs

• Inputs are what goes into a system to make it work, such as force, energy, or raw materials.
• Outputs are the tasks or services a system performs.
• A bicycle's input is the rider's downward force on the pedals, and the output is forward motion.
• A garden requires water, sunlight, fertilizer, and seeds as inputs to produce flowers, fruits, and vegetables as outputs.
• Ontario's health care system includes hospitals and doctor's offices as subsystems.
  • Inputs include doctors, money, and equipment.
  • Outputs include emergency operations, medicines, and counselling.

Side Effects and Systems Thinking

• Side effects are unintended or undesired outputs of a system.
• Car's desired output: motion; side effects: pollution and traffic.
• Systems thinking involves considering inputs, outputs, and side effects.
• Systems evolve due to changing living and social conditions and new technologies.

Waste Management System

• Waste management systems, like recycling and composting programs, help organize waste while considering the environment.

Telephone System

• Telephone systems have changed significantly due to technology and consumer needs.

Education Systems

• Education systems are deeply rooted in tradition, making change difficult but possible over time.

Simple Machines

• A simple machine requires a single force to work and consists of one or two parts; a stapler is an example.
• Six simple machines: inclined plane, wedge, screw, lever, wheel and axle, and pulley.
• These can be grouped into those related to the inclined plane (wedge and screw) and those related to the lever (wheel and axle and pulley).

Inclined Plane, Wedge and Screw

• Inclined plane: a flat, tilted surface; ramps and staircases are examples.
• Wedge: a movable inclined plane, like an axe.
• Screw: an inclined plane cut into a central core.

Levers

• Lever: a rigid bar that pivots at a fulcrum.
• The load arm is between the fulcrum and the load; the effort arm is between the fulcrum and where effort is applied.
• Levers are used in tools like scissors and door handles.
• Input force is applied by the user.
• Output force is the redirected push applied to the load.
• Load force (resistance) is what the user's input force must overcome.
• Levers are divided into three classes based on the positions of the fulcrum, load force, and input force.
  • Class 1: fulcrum is between the load force and input force.
  • Class 2: load force is between the fulcrum and the input force.
  • Class 3: input force is between the fulcrum and the load force.

Wheel and Axles, Gears, and Pulleys

• Wheel and axles, gears, and pulleys involve rotary motion as an input, output, or both.

Wheel and Axles

• Wheel and axle consist of a large diameter disk (wheel) attached to a small diameter shaft (axle).
• Turning the axle with the wheel changes a small input force into a larger output force.
• Wheel and axles can also work by applying a large input force on the axle to gain distance (e.g., spinning top).

Gears

• Gears are toothed wheels used to speed up or slow down, or change the direction of motion.

Pulleys

• Pulleys use wheels and axles to make pulling objects easier, helpful for lifting heavy loads or changing force direction.
• Can be used alone or create pulley systems with fixed and moveable pulleys.
• A fixed pulley is attached to a rigid structure, while a moveable pulley is not.

Fundamental Forces in Nature

• Four fundamental forces in nature: gravitational, electromagnetic, strong nuclear, and weak nuclear.

Gravitational Force

• Gravitational force (gravity) pulls objects towards Earth's surface.

Electromagnetic Force

• Electromagnetic force causes motions and activities in daily life.

Representing Forces

• Forces have magnitude (strength) and direction.
• Diagrams use arrows to represent forces, with the arrow's head indicating direction and length indicating magnitude.
• Force is measured in newtons (N).

Mass and Weight

• Mass is the amount of matter in an object.
• Weight is the force of gravity between two objects.
• Earth exerts a force of 9.8 N per kilogram of an object's mass (9.8 N/kg).
• The moon's gravity is about one-sixth of Earth's.
• An object's mass remains constant, but its weight would be less on the Moon.
• Overcoming gravity requires applying approximately 9.8 N of force or greater.

Friction

• Friction resists motion between objects in contact.
• Static friction prevents surfaces at rest from sliding.
• Sliding friction slows down moving objects.
• Lubricants minimize friction by allowing surfaces to slide more easily.

Mechanical Advantage (MA)

• Mechanical advantage is when a machine turns a small input force into a larger output force.
• MA = output force / input force
• Mechanical advantage of a lever can be estimated by comparing the lengths of the effort arm and load arm.
• A mechanical advantage can be less than 1, which happens when the input force is greater than the output force. A benefit of this is it increases the distance and speed of the output.
• Mechanical advantage can also be estimated by comparing input and output distances (MA = input distance / output distance).
• If input and output distances are the same, mechanical advantage is 1.

Ideal Mechanical Advantage vs Actual Mechanical Advantage

• Ideal mechanical advantage assumes all input force is converted to output force, which is never possible.
• Actual mechanical advantage is the ideal mechanical advantage minus forces lost to factors like friction, slippage, and distortion.
• Actual mechanical advantage is determined by measuring actual forces.
• Sensitivity of tools needs to vary based on force size and accuracy.

Work

• Scientific work is done when a force applied to an object causes it to move a distance parallel to the force.
• Work is calculated by multiplying force (in newtons) by distance (in meters).
• Work is measured in newton-meters (Nm), also known as joules (J), where 1 Nm = 1 J.

Work and Energy

• Energy is the ability to do work.
• The Sun provides energy to plants, which is then consumed by animals.
• Although energy is always consumed when work is done, not all of the energy consumed is turned into useful work
• Energy is measured in joules (J), and kilojoules (kJ) are used for larger amounts (1 kJ = 1000 J).