Of the hard sciences, physics is definitely my favorite. Biology is the most relatable and chemistry is possibly the most practical, but physics is the most philosophical. What is energy? What is matter? What is reality? How did it all begin? We’ll be debating these questions for a very long time.
Physics: The study of movement and energy. This includes the study of gravity, electricity, sound, light, magnetism, nuclear energy and more.
The theory of everything: A theory that has not yet been found that explains how all of the different theories and laws (such as the law of gravity and quantum physics ideas) can work together in the same universe, even though they seem to contradict each other. The main two theories of everything are general relativity and quantum field theory. General relativity is the theory that all events are caused by gravity, while quantum theory discusses the interplay of the strong force (subatomic particles), the weak force (gravity) and the electromagnetic force. These theories are separately confirmed, but seem to contradict; it seems that even though they are both correct, they cannot both be correct. Since general relativity is used for large-scale problems and quantum theory is used for small-scale problems, their incompatibility is usually avoided.
String theory: The current favorite theory of everything since it attempts to marry general relativity and quantum theory by proposing that the four fundamental forces were, at the time of the Big Bang, a single force, and every particle in the universe is, at the smallest level, a pattern of vibrating strings with its own vibration pattern.
Energy: The invisible, indescribable, mysterious thing that allows for movement and work. Energy is not made of particles and doesn’t have mass or volume. We cannot directly observe it, but only understand it through its effects. Note that everything in the Universe is made of either matter or energy. Note also that energy cannot be either created or destroyed; in order to get energy out of a system, you must first get it from somewhere else and put it in to the system. (It can convert into a different form, however.)
Energy conversion: A change in the form of energy from one type to another. For example, during photosynthesis, sun energy becomes stored energy, then kinetic energy used for growth.
Energy chain: The chain reaction that occurs as energy is converted to another form, then that energy is converted to another form, and so on.
Energy storing materials: Energy is stored in wood, fuel, batteries, light, food, etc.—anything that releases energy when burned. (Remember, food isn’t turned into energy. It stores energy, then releases it from the food.)
The two fundamental forms of energy: Potential (stored) and kinetic (moving)
Kinetic energy: Energy that is currently active, such as wind energy and the movement of water.
Potential energy (stored energy): Energy currently in storage, such as seed energy or the energy inside a full balloon. In order to have potential energy, the material must be in a position to be affected by a force, such as gravity.
Important types of energy: Chemical, electrical, mechanical, thermal, nuclear, gravitational, radiant, elastic and solar
Solar energy: The light and heat that radiates from the sun
Nuclear energy: The energy found in an atom’s nucleus
Heat energy: A form of energy that flows from one place to another because of a difference in temperature. It is really the motion of the particles that feel hot. (So in a way it’s kinetic energy.) Heat energy flows from hot to cool to even out, like air pressure moves from high to low and water flows downhill.
Chemical energy: Energy stored in the bonds of atoms and molecules. It is released in chemical reactions in the form of heat.
Electrical energy: The energy carried by electrons in an electric conductor.
Mechanical energy: The energy something has due to its motion
Thermal energy: The energy something has due to its heat levels (temperature)
Gravitational energy: The energy something has due to the effects of its gravitational field. Example: A raised hammer has gravitational energy that is converted to heat energy after it lowers and hits the nail.
Newton’s First Law of Motion: “A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force.”
Newton’s Second Law of Motion: “The force acting on an object is equal to the mass of that object times its acceleration.”
Newton’s Third Law of Motion: “For every action, there is an equal and opposite reaction.” Example: A balloon full of air is let go. The air goes one way and the balloon goes another.
Equilibrium: When forces or energies or systems are in balance
E=mc2: Energy equals mass times speed of light squared. This is the formula that Einstein discovered that shows the rate at which matter is converted into energy and vice versa.
Dynamics: The study of how forces affect movement
Freefall: Any motion of anything where gravity is the only “force” (source of movement) affecting it. Objects in freefall are weightless because nothing is pulling it toward itself. (This is also why the weight of objects are different on different planets: there is a different amount of gravity working on the object.)
Weightlessness: Freefall, but not quite, because the object is inside of something, such as a spacecraft
Drag/air resistance: Friction that occurs between air and any object moving through it. With no friction at all, objects falling toward the earth would fall at the same rate.
Velocity: Measurement of speed as well as the direction. Velocity changes when direction changes even when speed stays the same.
Terminal velocity: When something falls through gas or liquid it accelerates at a decreasing rate until it reaches its maximum constat velocity. This is terminal velocity. Happens when force of gravity equals air resistance to its falling.
Centripetal force: The “force” that causes something turn in a circle instead of in a straight line. It is not actually a force, but the net result of all the forces acting on the object that result in the circular movement.
Inertia: The property of a stationary object to remain stationary and a moving object to remain moving unless acted upon by another force. (Including friction and gravity.)
Friction: The resistance of one surface to slide over another. Friction is everywhere. Without it nothing would stop moving. Wheels lose less motion to friction because they don’t have to slide at any time. Oil reduces friction. Friction causes movement energy to be converted to heat energy. The movement energy isn’t loss, it’s transferred!
Hydrometer: Water displacement instrument of volume measurement
Surface tension: Sideways and downward attraction on a liquid’s surface. Happens because molecules in water at top are more attracted to molecules in water below than to molecules in the air.
Cohesion: When molecules of one substance are more attracted to each other than to the substance they’re touching. Ex: surface tension.
Adhesion: Opposite: Molecules are more attracted to substance they’re touching than to each other – ex: glue. Occurs often with liquids.
Diffusion: Molecules spread out to fill a space more evenly. Occurs often in gases.
Corrosion: Chemical reaction from metal contacting oxygen. Metal forms an oxide on the surface and gets tarnished.
Galvanizing: Covering metal with zinc. Done to car parts, etc.
Turbulence: The uneven movement caused when an object moves through air or water
Gyroscope: Wheel that spins fast within a frame and keeps frame from toppling over due to centripetal force
Generator: A device that uses kinetic energy to create electrical energy by using a turbine with magnet
Mass, Force and Gravity:
Force: Any push or pull on an object. This includes the force of gravity, the force of a human hand picking something up, and much more. All objects not in motion still have forces acting on them at all times, but when not moving, these forces are canceling each other out. For example, in order to sit still I must hold my body upright in a way that perfectly balances the force of gravity on it.
The four fundamental forces in the universe: The strong force (the nuclear force that holds subatomic particles together), the weak force (gravity, which is much less powerful than the strong force), the electromagnetic force, and the weak interaction (the force responsible for the radioactive decay of atoms).
Gravity: The force of nature that causes all things with mass or energy to move toward each other. This includes planets, stars, galaxies, electrons and even light. Gravity is what caused the planets to attract more particles and structures and grow larger. It holds heavenly bodies in orbit around each other, it causes the Moon to pull Earth’s water toward it, creating tides, and it gives things on Earth weight. It is sometimes called the “weak force,” (referring to the four fundamental forces of physics) even though it is not actually a force at all.
Albert Einstein’s General Theory of Relativity: Gravity is not a force. It has no inherent power. It is not energy. It is a simple result of the curvature of spacetime which in turn is caused by the uneven distribution of mass across the universe.
Matter: Anything that is made of particles, takes up space (has volume), and has mass. In other words, matter is everything except energy.
Volume: A measurement of the amount of space something takes up
Weight: A measurement of how resistant something is due to the forces (gravity or other forces) that try to hold it in place
Mass: A measurement of something’s absolute heaviness that doesn’t change when the forces (such as the gravitational force) change
How to measure mass: One liter of water has a mass of one kilogram. Anything we measure the mass of, we compare to the mass of one kilo of water. If the water were on the moon, and we compare it to a book, the number ( plus or minus the kilo of water) is same as it would be on earth.
Density: The measurement of something’s mass per unit of volume. Dense objects are heavier than other, less dense objects that take up the same amount of space.
Black hole: A supercondensed, superheavy space body whose gravity pulls in everything near it and from which nothing, not even light, can escape.
Event horizon: The place near a black hole from which everything is irrevocably pulled into the black hole
Electricity and Magnetism:
Electricity: The effect caused by the presence and movement of charged particles (specifically, the electrons in the charged particles)
Electromagnetism: The term denoting the entire force of electricity and magnetism, both of which occur between electrically charged particles. This force is commonly shown as a spectrum, with visible light in the center, which is known as the electromagnetic spectrum.
Electromagnetic wave: Air waves made of continually changing electric and magnetic fields that can move through solids, liquids, gases and even a vacuum.
Electromagnetic spectrum/radiant energy: All parts of the electromagnetic spectrum, whether or not they are visible to the human eye, including (in order): gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, radar, FM, TV, shortwave and AM.
Electric field: An area in space that surrounds an electric charge or an electromagnetic wave that exerts force on other charges
Electric current: A flow of electric charge
Conductor: An object or material that allows an electrical current to flow in one or more directions
Insulator: An object or material that does not allow an electrical current to flow freely or easily through it
Static electricity: An imbalance of electrical charges causing some charges to seek a path away from their present location
Magnet: A material or object that produces a magnetic field
Magnetic field: All the (invisible) space around a magnet that attracts iron. The field is strongest at the poles. Note on Earth’s magnetic field: The Earth acts as a huge magnet. There is a magnetic field around Earth. Not strong enough to pull all iron to the poles, but strong enough that magnets with reorient to be parallel to the field. This is why compasses work.
Properties of magnets: 1. They only act on iron and iron-containing materials; 2. They have two ends, or poles (north-seeking and south-seeking); 3.They have a magnetic field; 4. Opposite pole attract, like poles repel (though both ends are attracted to iron); 5. Their magnetic fields pass through the other materials.
Ferromagnetism: The magnetic quality of certain materials (such as iron) that allows them to permanently attract or repel. (There are also many other materials that have a magnetic quality, but more weakly and not permanently.)
Magnetic north/south: The magnetic poles of the earth, which is a huge magnet. (These poles are slightly different from the geographical North Pole and South Pole.)
Light: A form of energy made up of electromagnetic waves
Visible light spectrum: The parts of the spectrum that are visible to the human eye/mind connection. Visible light is a very small part of the light spectrum.
Speed of light: The speed that light travels in a vacuum (over 186,000 miles per second). It is also the highest possible speed at which all other massless particles can travel including gravitational waves and electromagnetic energy. (Particles with any amount of mass can never reach this speed.)
Luminous: The giving off of light (as opposed to the mere reflecting of light) by an object
Light intensity: The measurable amount of light (or another property) present
Translucent: Almost entirely see-through
Opaque: Not see-through
Umbra: The darkest part of a shadow
Penumbra: The faded part of a shadow
Laser: Machine that creates a beam of intense pure color of one wavelength and frequency. Its waves are coherent—travel in step with each other and stay in a narrow beam. Lots of energy is transported in a small space.
Color: The parts of light rays that become visible when light reflects off an object. The human eye can’t see the light rays that gets absorbed by the same object. Since every object absorbs light differently, objects reflect light differently, too.
Fluorescence: The property of some substances that cause them to glow when exposed to light. This occurs because the material is able to absorb high-frequency wavelengths, like UV light, which is invisible to the human eye, but then emit visible light from that absorbed light. UV light works best to create the glow effect because it is a high-energy frequency. Note that some energy is lost in the energy conversion process, so high-energy frequency is needed so there’s enough energy left after conversion to cause the glow.
Phosphorescence: The property of some substances that cause them to glow. Unlike a fluorescent material, though, a phosphorescent material doesn’t immediately re-emit the radiation it absorbs; instead, it can re-emit it up to several hours after the absorption. Examples include glow-in-the-dark paint or toys. The reason for this ability to hold the energy has to do with quantum mechanics.
Dispersion: For example, at sunrise and sunset light has to travel through more of the atmosphere before reaching your eyes. Blue is scattered before you see it, leaving lower frequency red and orange.
Prism: An object, such as a diamond or a piece of cut glass, that bends the white light that hits it, thereby splitting it and causing a rainbow to appear
Convex lens: A lens that is shaped like an upside-down bowl
Concave lens: A lens that is shaped like a bowl
Mirror: A piece of glass with a silver-painted backing behind it that causes all light to reflect back to the viewer
Converging lens: A lens that converges rays of light that are traveling parallel to its principle axis. This kind of lens corrects farsightedness.
Diverging lens: A lens that diverges rays of light that are traveling parallel to its principle axis. This kind of lens corrects nearsightedness.
Reflection: The bouncing of waves off a surface and back the opposite direction
Refraction: The change in path of a wave. We see light waves change path when we put a straw in a glass of water. The straw appears bended due to the changing of the path of light when traveling through air to traveling through water and vice versa.
Interference: The changing of a wave’s path resulting from an outside force
Constructive interference: The increase in a wave’s size due to interference
Destructive interference: The decrease in a wave’s size due to interference
Diffraction: The splitting of light waves into two or more separate light waves when passing through small openings or encountering an obstacle
Three types of heat transfer: Convection, conduction and radiation
Convection: Heat transfer through moving gases or liquids, such as ocean currents or warm air currents
Conduction: Heat transfer through solids using direct contact, such as a pan on a burner
Radiation: Heat transfer through the air or through space, such as the sun heating the atmosphere or a radiator heater heating a home’s air. The air does not have to be moving to transfer the heat energy.
Sound: The vibration that occurs in a hearing ear after sound waves contact it. Sound waves are only sound if they find a hearing ear. The sound waves bump the particles in the air and transfer the movement energy from particle to particle till it gets to the ear. (Note: Sound waves transfer movement energy while light waves travel as electromagnetic radiation. Sound will only travel through gas, liquid or solid, but not through a vacuum – no particles are there to transfer the energy. Light does, though, and thus it moves much faster than sound – 186,000mps rather than .2mps.)
Sound vibrations: sometimes included as a form of energy.
Sound wave: The wave pattern of sound vibrations
Vibrations: Fast back and forth movements of any kind
Tone: Any prolonged sound note
Pitch: the specific note (A, B-flat, etc) – Made by tightening or loosening vocal cords, guitar strings, etc. and slowing or speeding up the vibrations.
Sound intensity: The loudness of the sound
Frequency: the speed of the vibration. High f=fast, low f=slow.
More tension = faster vibration = higher frequency = higher pitch.
Amplitude: Distance traveled from one side to another of the sound wae. More distance = louder sound.
How sound is made from voices: By passing air through the larynx and at the same time putting tension on the vocal cords. (To feel the vibration, touch the throat while talking.)
Echoes: Result of sound waves bumping hard surfaces and changing directionsTelephones change sound vibrations into electric signals. Same with cell phones, etc. Changed back to sound waves at the listener’s end.
Human ear can only vibrate/pick up 20-20,000vibrations per second frequencies.
Infrasound: Sounds at frequencies below the ability of humans to hear it
Ultrasound: Sounds at frequencies above the ability of humans to hear it
Sonic boom: The sudden crashing sound that results when a noise breaks the sound barrier
Echo location: The ability of some animals, such as bats, to locate solid objects by emitting sound and hearing the echo come back to them; a sense
Sonar: A way of bouncing ultrasound waves off far-away objects to determine their location
Nuclear power: Using controlled nuclear energy for power, either from fusion (marrying of nuclei) or fission (splitting in half of nuclei).
Nuclear weapons: Produce uncontrolled nuclear reactions. Atomic bombs use fission, hydrogen bombs use fusion.
Nuclear reactor: Nuclei are bombarded with neutrons and split (fission). Energy is harnessed for use.
Radioactivity: When a substance’s atoms release nuclear energy as radiation.
Renewable energy: Energy derived from renewable resources [move to ECOLOGY]
Renewable resource: A natural resource that renews itself fast enough to keep up with human rates of use. These include sunlight, wind, rain, tides, waves and geothermal heat.
Non-renewable resource: A natural resource that does not renew itself fast enough to keep up with human rates of use. These include minerals, metal ores, fossil fuels (coal, petroleum and natural gas) and some groundwater.
Fossil fuel: A fuel derived from organic fossils (decayed plants and animals with highly concentrated energy) deep inside the Earth
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