Understanding Force and Friction

• Force is a push or pull that can change the speed, direction, or shape of an object

Types of Forces

• Contact forces, such as friction, require direct contact between objects
• Non-contact forces, such as gravity and magnetism, act at a distance

Units of Force

• In the MKS system, force is measured in Newtons (N)
• In the CGS system, force is measured in dynes (d), where 1 dyne = 10^-5 Newtons
• In the English system, force is measured in pounds (lb)
• Spring balance is used to measure forces

Concurrent Forces

• Concurrent forces are forces acting at one point
• Resultant force is the combined effect of all the forces applied
• Equilibriant force is equal in magnitude to the resultant force but acts in the opposite direction
• Friction is the resistance encountered when one body is moved against another

Types of Friction

• Static friction occurs between stationary surfaces
• Sliding friction occurs between sliding surfaces
• Rolling friction occurs between rollers

Laws of Motion

• Law of Inertia: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force; net resultant force is zero (state of inertia)
• Law of Acceleration: When an unbalanced force acts on an object, it accelerates in the direction of the force; acceleration is directly proportional to the force and inversely proportional to the mass of the object, with the equation F = m x a; weight is mass x acceleration due to gravity, W = m x g, where g = 9.8 m/s²
• Law of Action & Reaction: For every action, there is an equal and opposite reaction; F action = - F reaction

Work and Power

• Work = Force x displacement
• Unit of work: MKS is Joules (Newton-meter), CGS is Ergs (10^-7 Joules), English is foot-pound
• Force must be in the same direction as the displacement; if force is perpendicular to displacement, work = 0; if displacement = 0, work = 0
• Displacement vs. Distance: Both measure changes in position, but distance is path-dependent, while displacement is position-dependent
• Power = Work / time = Force x velocity
• Unit of power: watts = Joule/sec; 1 horsepower = 746 watts

Simple Machines

• Lever: A simple machine with three classes, each varying by the location of the fulcrum, resistance, and effort
• 1st Class Lever: Fulcrum is between resistance and effort
• 2nd Class Lever: Resistance is between fulcrum and effort
• 3rd Class Lever: Effort is between resistance and fulcrum
• Law of Lever: (Force/Effort) x Effort arm = Resistance x Resistance arm

Other Simple Machines

• Inclined plane
• Pulley
• Wedge
• Wheel and axle
• Screw

Energy

• Energy: The ability or capacity to do work; measured in Joules (MKS) or Ergs (CGS)
• Potential Energy (PE): Energy due to position or shape ("stored energy"); maximum when KE = zero; a body in motion still has PE
• Gravitational PE (GPE): "energy at rest"; GPE = mgh
• Elastic PE (EPE): EPE= ½ kx² (k = spring constant, x = displacement of spring)
• Kinetic Energy (KE): Energy in motion; KE = ½ mv²; at rest, KE = 0; KE max when PE = zero

Law of Conservation of Energy

• The total amount of energy isolated from the rest of the universe remains constant but can change from one form to another
• Energy can neither be created nor destroyed, it can only change from one form to another
• Internal Energy (U): Sum of kinetic and potential energy; U = KE + PE (PE increases as KE decreases and vice-versa)

Flow of Energy

• Conduction: Transfer of energy by direct contact
• Convection: Transfer of energy by the movement of hot fluid from one place to another
• Radiation: Transfer of heat energy through light rays

Matter

• Matter is anything that occupies space (volume) and has mass, possessing density
• Physical Properties: Properties observed without changing the substance

Types of Physical Properties

• Intensive properties: Independent of the amount of matter (e.g., density, odor, taste)
• Extensive properties: Dependent on the amount of matter (e.g., mass, volume, length)
• Chemical Properties: Properties identified when a substance reacts with another substance

Classification of Matter

• Pure Substances: Elements, the simplest substances, can't be decomposed by ordinary chemical means, and compounds, which are combinations of two or more elements chemically combined and decomposable

Elements

• Metals are good conductors of heat and electricity
• Non-metals have low density and don't conduct heat & electricity
• Metalloids possess properties of both metals and non-metals
• Organic compounds primarily contain carbon atoms, especially carbon-hydrogen bonds
• Inorganic compounds do not contain carbon-hydrogen bonds, but may include carbon (e.g., table salt (NaCl), carbon dioxide (CO2), diamond (pure carbon), carbonates, cyanides, carbides)

Mixtures

• Combination of two or more substances physically mixed, separable by physical means
• Filtration or sedimentation
• Distillation involves vaporizing and condensing components of a liquid mixture. Evaporation involves heating until liquid evaporates. Decantation separates liquid from solid
• Chromatography involves dissolving mixture in fluid solvent

Homogenous Mixtures

• Homogeneous mixtures have only one observable phase, like alloys (brass, bronze, solder, steel), solutions, or gases
• Solutions consists of solute and solvent
• Concentrated solution has more solute than solvent
• Diluted has more solvent than solute
• Saturated has equal amounts of solute and solvent
• Supersaturated contains more solute than solution allows

Heterogenous Mixtures

• Heterogeneous mixtures have multiple observable phases
• Suspensions have particles that settle out
• Colloids exhibit Tyndall effect
• Emulsions are immiscible colloidal suspensions
• Aerosols are suspensions of particles in gas

Fundamental States of Matter

• Solid
• Liquid
• Gas
• Plasma

Other States of Matter

• Superconductor: Zero electrical resistivity and perfect conductivity
• Superfluid: Close to absolute zero, zero viscosity
• Fermionic Condensate: Similar to BEC but composed of fermions
• Quantum Hall State: Quantized Hall voltage measured perpendicular to current flow

High Energy States

• Degenerate Matter: Under extremely high pressure supported by quantum mechanical effects
• Quark Matter or Quantum Chromodynamical (QCD): Quark matter phases occur at extremely high densities or temperatures
• Color-Glass Condensate: Theorized to exist in atomic nuclei traveling near the speed of light.

Physical Properties of Matter

• Malleability: Ability of metals to be flattened into sheets
• Ductility: Ability of metals to be drawn into wires
• Elasticity: Ability of an object to be stretched and return to original shape
• Solubility: Amount of solute that dissolves in a given amount of solvent
• Surface Tension: Property of liquid that draws molecules into the body minimizing surface area
• Viscosity: Resistance of fluid to flow
• Capillarity: Ability of liquids to rise through tubes
• Luster: the ability of metals to reflect light
• Hardness: the ability to not be scratched or cut
• Brittleness: the ability to break under tension
• Porosity: capacity of some materials to absorb or release liquids or gases
• Permeability: the ability of matter to allow water/liquids to pass through them

Chemical Properties of Matter

• Flammability: Easily ignites at ambient temperatures
• Combustibility: Can burn in air under certain conditions
• Reactivity: Tendency to combine chemically with other substances
• Toxicity: Extent to which a chemical element or chemical may harm an organism
• Chemical Stability: Thermodynamic stability of a chemical system
• Acidity: Ability to react with an acid

Changes in Matter

• Physical Change: Involves change in state, size, shape, or physical appearance
• Chemical Change: Results in the formation of a new substance
• Diffusion: Ability of matter to spread quickly
• Brownian Motion: Refers to the random motion of particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium
• Exothermic Reaction: Releases heat to the environment
• Endothermic reaction is a chemical reaction that absorbs heat from the surroundings

Geology

• Geology: Study of the Earth
• Atmosphere: Gas envelope; 78% nitrogen, 21% oxygen, 1% other gases

Layers of Atmosphere

• Troposphere
• Stratosphere (Ozone layer)
• Mesosphere
• Thermosphere
• Hydrology: Study of water on and within the earth
• Lithosphere: Solid part
• Continental Drift: Theory proposed by Alfred Wegener
• Plate Tectonics: Lithosphere divided into plates that are constantly moving
• Seismology: Study of earthquakes

Materials of the Earth

• Igneous rocks: Formed by cooling and hardening of magma
• Intrusive solidify beneath Earth
• Extrusive cooled from lava
• Sedimentary Rocks: Deposited at bottom of bodies of water
• Minerals: Naturally formed solid elements or compounds having a crystalline structure
• Mineralogy: Science that deals with identification and classification of compounds
• Hardness: Resistance of a mineral to being scratched
• Weathering: The breaking down of rocks

Cycles in the Ecosystem

• Water, Carbon-Oxygen, Nitrogen, and Phosphorus Cycles
• Species interactions in ecosystems includes Symbiosis, Mutualism, Commensalism, Parasitism, Predation, Competition, and Cooperation

Scientific Method

• Statement of the Problem
• Gather Relevant Data & Information
• Formulate the Hypothesis
• Perform the Experiment
• Independent Variables: the factors that have affect on the data
• Dependent Variables: Factors that is measured from the data
• Controlled Group: Group of tests where nothing is changed
• Make Observations
• Draw the Conclusion