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PHYSICS MEGATHREAD
From Newton to Quantum Mechanics
INTRO
alr n*****s, this is the best GUIDE u will ever see in any forum
You don't need to be some 333 IQ mathematician to understand the basic ideas. Most of physics is basically:
observe something --> find a pattern --> describe it with math --> test whether it actually works.
I'm going from the absolute basics into some of the more insane shit like relativity, quantum mechanics, black holes and particle physics.
this took me a shit ton of time so PLS REP IT NIGGERRR
Physics is the study of matter, energy, space, time, and the interactions between them.
Pretty much everything physical falls somewhere inside it.
Motion?
Physics.
Light?
Physics.
Electricity?
Physics.
Stars?
Physics.
Why your phone works?
Physics.
Why the universe behaves the way it does?
Also physics.
Some major areas of physics include:
• Classical mechanics
• Electromagnetism
• Thermodynamics
• Optics
• Relativity
• Quantum mechanics
• Nuclear physics
• Particle physics
• Astrophysics
• Cosmology
The funny thing is that these aren't completely separate subjects.
They overlap constantly.
2. UNITS & MEASUREMENT
Before doing physics, you need to be able to describe quantities.
The standard system is SI units.
Length → meter (m)
Time → second (s)
Mass → kilogram (kg)
Temperature → kelvin (K)
Electric current → ampere (A)
From these, we construct other units.
Velocity → m/s
Acceleration → m/s²
Force → newton (N)
1 N = 1 kg·m/s²
Units are actually extremely useful because they can catch mathematical mistakes.
If you're calculating a velocity and somehow end up with kg/s, you've probably fucked something up.
3. SCALARS VS VECTORS
A scalar only has magnitude.
Examples:
• mass
• temperature
• energy
• time
• speed
A vector has magnitude AND direction.
Examples:
• velocity
• acceleration
• force
• displacement
• momentum
For example:
60 km/h
is a speed.
60 km/h north
is a velocity.
Same magnitude, but velocity also tells you the direction.
4. KINEMATICS
Kinematics describes motion without worrying about what causes the motion.
The basic quantities are:
position
velocity
acceleration
Velocity describes how quickly position changes.
v = Δx / Δt
where:
v = velocity
Δx = change in position
Δt = change in time
So if something travels 100 meters in 5 seconds:
v = 100 / 5
v = 20 m/s
simple.
5. ACCELERATION
Acceleration is the change in velocity over time.
a = Δv / Δt
If a car goes from:
0 m/s --> 20 m/s
in 5 seconds:
a = 20 / 5
a = 4 m/s²
That means its velocity increases by about 4 m/s every second.
Acceleration doesn't necessarily mean "speeding up."
An object can accelerate while slowing down or changing direction.
6. NEWTON'S LAWS
Now we get into the GOAT of classical mechanics.
Sir Isaac Newton.
NEWTON'S FIRST LAW
An object remains at rest or continues moving at constant velocity unless acted upon by a net external force.
Basically:
objects don't randomly change their motion.
A stationary object stays stationary.
A moving object keeps moving at constant velocity.
Something has to interact with it to change that.
This is called inertia.
NEWTON'S SECOND LAW
The famous one:
F = ma
Force equals mass times acceleration.
This tells you how force, mass and acceleration are related.
More force --> more acceleration.
More mass -->less acceleration for the same force.
Example:
A 10 kg object experiences a 20 N net force.
a = F / m
a = 20 / 10
a = 2 m/s²
NEWTON'S THIRD LAW
For every action, there is an equal and opposite reaction.
If you push a wall, you exert a force on the wall.
The wall exerts an equal and opposite force on you.
If you jump, you push the Earth downward.
The Earth pushes you upward.
The Earth is obviously so massive that its acceleration is basically negligible compared with yours.
7. GRAVITY
Near Earth's surface, objects accelerate downward at approximately:
g = 9.81 m/s²
Ignoring air resistance, a dropped object accelerates at roughly this rate.
After 1 second:
9.8 m/s
After 2 seconds:
19.6 m/s
After 3 seconds:
29.4 m/s
etc.
The important thing is that mass doesn't determine the acceleration of a freely fallingobject near Earth's surface.
A 1 kg object and a 10 kg object fall at approximately the same acceleration in vacuum.
Air resistance is why things like feathers don't behave the same way in Earth's atmosphere.
8. UNIVERSAL GRAVITATION
Newton didn't stop at Earth's gravity.
He proposed:
F = G(m₁m₂ / r²)
where:
G = gravitational constant
m₁ and m₂ = masses
r = distance between their centers of mass
This tells us that gravitational force:
increases with mass
and decreases with the square of distance.
Double the distance:
1/4 the gravitational force.
Triple the distance:
1/9 the force.
This equation worked insanely well for centuries.
Then Einstein came along.
9. WORK
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In physics, work has a very specific meaning.
Work occurs when a force causes displacement.
W = Fd cosθ
where:
W = work
F = force
d = displacement
θ = angle between the force and displacement
If you push a box forward, you're doing work on it.
If you're holding a heavy object completely stationary, you're exerting force but doing zero mechanical work on the object because it isn't moving.
Physics definitions can be annoying like that.
10. ENERGY
Energy is one of the most important concepts in physics.
There are many forms:
• kinetic energy
• gravitational potential energy
• thermal energy
• chemical energy
• electrical energy
• nuclear energy
• electromagnetic energy
Energy can be transferred and transformed.
But the total energy of an isolated system is conserved.
This is the law of conservation of energy.
11. KINETIC ENERGY
The energy associated with motion:
KE = ½mv²
Notice the velocity is squared.
That means doubling velocity gives four times the kinetic energy.
A 2× increase in velocity:
2² = 4
so:
4× kinetic energy.
This is one reason why increasing speed dramatically increases the energy involved in collisions.
12. POTENTIAL ENERGY
Potential energy is stored energy associated with a system's configuration.
Near Earth's surface:
PE = mgh
where:
m = mass
g = gravitational acceleration
h = height
Raise something higher:
more gravitational potential energy.
Drop it:
that energy can become kinetic energy.
This is basically energy constantly changing forms.
13. MOMENTUM
Momentum is:
p = mv
Mass × velocity.
Momentum is conserved in isolated systems.
This becomes extremely important when studying collisions.
A massive truck moving slowly can have enormous momentum.
A tiny object moving extremely fast can also have significant momentum.
Momentum isn't the same thing as kinetic energy either.
They're related, but different quantities.
14. COLLISIONS
There are different types of collisions.
ELASTIC COLLISION
Momentum is conserved.
Kinetic energy is also conserved.
INELASTIC COLLISION
Momentum is conserved.
Kinetic energy isn't necessarily conserved as kinetic energy.
Some becomes:
• heat
• sound
• deformation
• other forms of energy
A completely inelastic collision is when objects stick together after colliding.
15. CIRCULAR MOTION
An object moving in a circle is accelerating even if its speed stays constant.
Why?
Because velocity includes direction.
The direction is continuously changing.
The inward acceleration is called centripetal acceleration:
a = v² / r
where:
v = speed
r = radius
The corresponding force is:
F = mv² / r
Important:
centripetal force isn't a new fundamental force.
It's simply the name for whatever net force is pointing toward the center of the circular path.
Gravity can provide centripetal force.
Tension can.
Friction can.
etc.
16. ROTATIONAL PHYSICS
Things don't just move linearly.
They can rotate.
Rotational physics has analogues to ordinary mechanics.
Linear:
F = ma
Rotational:
τ = Iα
where:
τ = torque
I = moment of inertia
α = angular acceleration
Torque is basically the rotational equivalent of force.
Push a door near its hinge:
not very effective.
Push it near the handle:
much easier.
Same basic force, different torque.
17. WAVES/
A wave is a disturbance that transfers energy.
Waves can be:
• mechanical
• electromagnetic
Mechanical waves require a medium.
Sound is an example.
Electromagnetic waves don't require a material medium.
Light is an example.
Important wave quantities:
wavelength (λ)
frequency (f)
amplitude
speed (v)
And:
v = fλ
Higher frequency with the same wave speed means shorter wavelength.
18. SOUND
Sound is a mechanical wave.
In air, it's generally a longitudinal pressure wave.
The particles oscillate roughly parallel to the direction the wave travels.
Frequency determines the perceived pitch.
Higher frequency -->higher pitch.
Amplitude is related to the intensity of the sound.
Speed of sound depends on the medium and its properties.
In air at ordinary conditions it's roughly:
343 m/s
but it changes with temperature and other factors.
19. LIGHT
Light is electromagnetic radiation.
The electromagnetic spectrum includes:
• radio
• microwave
• infrared
• visible light
• ultraviolet
• X-rays
• gamma rays
They're all electromagnetic waves.
The main difference is frequency and wavelength.
Visible light is only a tiny portion of the electromagnetic spectrum.
20. ELECTRICITY
Electric charge comes in positive and negative forms.
Like charges repel.
Opposite charges attract.
The SI unit of charge is the coulomb (C).
Electric current measures the rate of charge flow:
I = Q / t
where:
I = current
Q = charge
t = time
Current is measured in amperes.
21. VOLTAGE
Voltage is electric potential difference.
A useful analogy is pressure in a fluid system.
It's not perfect, but it helps.
Voltage provides the potential difference that can drive current through a circuit.
One of the most famous equations:
V = IR
Ohm's law.
V = voltage
I = current
R = resistance
Increase voltage while resistance stays constant:
current increases.
Increase resistance while voltage stays constant:
current decreases.
22. ELECTROMAGNETISM
Electricity and magnetism aren't actually completely separate forces.
They're aspects of one electromagnetic interaction.
Moving charges produce magnetic fields.
Changing magnetic fields can produce electric fields.
This connection is described by Maxwell's equations.
Maxwell's work was absolutely massive for physics.
It showed that electromagnetic waves exist and that light itself is electromagnetic radiation.
23. THERMODYNAMICS
Thermodynamics studies heat, temperature, energy and entropy.
THE ZEROTH LAW
If A is in thermal equilibrium with B, and B with C, then A and C are in thermal equilibrium.
Basically:
temperature is transitive.
THE FIRST LAW
Energy is conserved.
A common form is:
ΔU = Q - W
depending on the sign convention being used.
Internal energy can change through heat transfer and work.
THE SECOND LAW
Entropy of an isolated system tends to increase.
This gives us the direction of many physical processes.
Heat naturally flows from hotter objects toward colder objects.
You don't normally see a cold drink spontaneously becoming colder while heating the room.
THE THIRD LAW
As a system approaches absolute zero, its entropy approaches a minimum under appropriate conditions.
Absolute zero:
0 K
approximately:
−273.15°C
24. ENTROPY
Entropy gets explained badly online all the time.
It's not simply:
"disorder."
That's a useful beginner analogy, but incomplete.
More fundamentally, entropy is related to the number of microscopic configurations consistent with a macroscopic state.
Boltzmann gave us:
S = k ln Ω
where:
S = entropy
k = Boltzmann constant
Ω = number of accessible microstates
This is where thermodynamics starts connecting with statistical mechanics.
25. SPECIAL RELATIVITY
Now we're leaving Newton behind.
Einstein's special relativity is based on two major ideas:
Time isn't universal.
Distances aren't universal.
Simultaneity isn't universal.
They're dependent on the observer's state of motion.
26. TIME DILATION
A moving clock is observed to run slower relative to a given inertial frame.
The Lorentz factor is:
γ = 1 / √(1 − v²/c²)
As velocity v approaches the speed of light c, γ becomes very large.
You can't accelerate a massive object to the speed of light.
The energy required approaches infinity in special relativity.
So:
massive objects cannot reach c.
Light doesn't have this problem because photons are massless.
27. LENGTH CONTRACTION
Objects moving relative to an observer are measured to be shorter along their direction of motion.
The relationship is:
L = L₀ / γ
where:
L₀ = proper length
Again:
this isn't simply an optical illusion.
It's a consequence of spacetime geometry.
28. MASS–ENERGY EQUIVALENCE
The famous equation:
E = mc²
(if u really reading this PM me and ill teach u other cool shit)
means mass is associated with energy.
Even a tiny amount of mass corresponds to a huge amount of energy because c² is enormous.
This relationship is fundamental to nuclear physics.
29. GENERAL RELATIVITY
Special relativity deals with inertial frames and high speeds.
General relativity brings gravity into the picture.
Einstein's big idea:
gravity isn't simply a conventional force.
Mass and energy curve spacetime.
Objects then move through that curved spacetime.
A common analogy is a heavy ball deforming a rubber sheet.
It's useful, but imperfect because actual spacetime has four dimensions and isn't literally a rubber sheet.
The basic idea:
matter tells spacetime how to curve,
and curved spacetime tells matter how to move.
30. BLACK HOLES (for the black holes I asked ai to give me info so I could read it and put what I understood here)
If enough mass is compressed into a sufficiently small region, you can form a black hole.
The boundary surrounding it is called the event horizon.
Once something crosses the event horizon, it cannot send information back out to distant observers through ordinary causal paths.
Black holes aren't cosmic vacuum cleaners.
If the Sun were somehow replaced by a black hole of exactly the same mass, Earth's orbit would initially remain essentially the same.
We'd have a much bigger problem because we'd lose sunlight.
31. QUANTUM MECHANICS
Now we get into the part where classical intuition starts getting absolutely destroyed.
Quantum mechanics describes nature at microscopic scales.
Atoms.
Electrons.
Photons.
Quarks.
etc.
Some quantities come in discrete amounts.
Particles can behave like waves.
Waves can behave like particles.
And measurement plays a fundamental role in quantum theory.
32. WAVE-PARTICLE DUALITY
Electrons aren't simply tiny classical balls.
They can produce interference patterns like waves.
Photons also exhibit both particle-like and wave-like behavior.
The famous double-slit experiment demonstrates this beautifully.
Send particles through two slits.
Even when particles are sent one at a time, the accumulated results can form an interference pattern.
That's fucking weird.
And it's real.
33. THE UNCERTAINTY PRINCIPLE
Heisenberg's uncertainty principle is commonly written:
ΔxΔp ≥ ħ/2
You cannot simultaneously know position and momentum with arbitrary precision.
This isn't simply a limitation caused by bad measuring equipment.
It's built into quantum mechanics itself.
The more precisely certain pairs of quantities are defined, the less precisely the corresponding conjugate quantity can be defined.
34. QUANTUM SUPERPOSITION
A quantum system can exist in a superposition of possible states.
Before measurement, its quantum state can contain multiple possible outcomes.
This doesn't simply mean:
"the particle is literally doing every classical thing at once."
Quantum mechanics describes the system using a state that contains amplitudes for possible measurement outcomes.
The mathematical formalism is weird.
But it works.
Insanely well.
35. QUANTUM ENTANGLEMENT
Two quantum systems can become entangled so that their measurement outcomes are correlated in ways that cannot be explained by ordinary classical hidden variables.
Measure one and you gain information about the other.
Einstein famously disliked the implications and referred to it as:
"spooky action at a distance."
Important though:
entanglement does NOT let you send usable information faster than light.
No FTL Discord messaging unfortunately.
36. THE STANDARD MODEL
Particle physics describes the known elementary particles and their interactions through the Standard Model.
MATTER PARTICLES
QUARKS:
• up
• down
• charm
• strange
• top
• bottom
LEPTONS:
• electron
• muon
• tau
• electron neutrino
• muon neutrino
• tau neutrino
FORCE-CARRYING PARTICLES:
• photon
• gluons
• W bosons
• Z boson
and the:
Higgs boson
The Standard Model is one of the most successful scientific theories ever created.
But it isn't a complete theory of everything.
37. THE HIGGS BOSON
The Higgs field exists throughout space.
Elementary particles interact with this field to different degrees.
The Higgs boson is an excitation of that field.
It was experimentally discovered at CERN in 2012.
And no:
the Higgs boson does not give literally everything mass.
For example, most of the mass of ordinary protons and neutrons comes from the energy associated with the strong interaction inside them, rather than directly from the Higgs mechanism.
38. NUCLEAR PHYSICS (AI helped me understand this shit cuz Im bad at nuclear physics sorry)
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Atomic nuclei contain:
protons + neutrons
These are collectively called nucleons.
There are two major nuclear processes worth knowing:
FISSION
A heavy nucleus splits into smaller nuclei.
This can release energy.
FUSION
Light nuclei combine into heavier nuclei.
This can also release enormous amounts of energy.
The Sun is powered by nuclear fusion.
39. ANTIMATTER
Most matter particles have corresponding antiparticles.
For example:
electron → positron
proton → antiproton
When matter and antimatter particles meet, they can annihilate into other forms of energy and particles while conserving the relevant quantities.
Why there is so much more matter than antimatter in our observable universe is still a major question in physics.
40. DARK MATTER
We have strong evidence that there is more gravitationally interacting matter in the universe than the matter we can see directly.
Galaxies rotate in ways that don't match the amount of visible matter alone.
Gravitational lensing also provides evidence.
Something appears to be contributing additional gravitational effects.
We call the unknown component:
dark matter.
We know a lot about what it does gravitationally.
We still don't know exactly what it is.
41. DARK ENERGY
The expansion of the universe is accelerating.
Whatever is responsible for this accelerated expansion is commonly called:
dark energy.
We don't currently have a complete understanding of its fundamental nature.
The simplest explanation is a cosmological constant associated with vacuum energy.
But this is still an active area of research.
42. THE UNIVERSE
The observable universe is big af
Galaxies.
Stars.
Planets.
Nebulae.
Black holes.
Dark matter.
And probably a whole lot of shit we haven't discovered yet.
The universe is expanding.
This doesn't mean galaxies are simply flying through pre-existing empty space from one central explosion.
On sufficiently large scales, space itself is expanding.
The Big Bang model describes the early hot, dense state of our observable universe and its subsequent expansion.
It doesn't necessarily answer the philosophical question:
"what happened before the Big Bang?"
idk n****r im not God so I cant say
43. WHY PHYSICS IS SO FUCKING INTERESTING TO ME
The crazy thing about physics is how much can come from a relatively small number of principles.
Newtonian mechanics explains an enormous range of everyday motion.
Maxwell's equations unify electricity and magnetism.
Thermodynamics explains heat and energy transfer.
Relativity changes our understanding of space and time.
Quantum mechanics describes the microscopic world.
And modern physics is still incomplete.
We don't yet have a fully accepted quantum theory of gravity.
We don't know exactly what dark matter is.
We don't know the fundamental nature of dark energy.
We don't completely understand why the observable universe contains vastly more matter than antimatter.
There is still an insane amount left to figure out.
44. FINAL TL;DR
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Physics starts with some pretty simple ideas:
motion
forces
energy
momentum
waves
electricity & magnetism
thermodynamics
relativity
quantum mechanics
particle physics
cosmology
if u get really interested in ts u willl most likely start asking ur self:
What is space?
What is time?
Why does gravity exist?
What is dark matter?
Why is there something rather than nothing?
That's basically why physics is so fucking cool.
You start with:
F = ma
and somehow end up talking about curved spacetime, quantum fields and the origin of the universe.
RESOURCES
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If you actually want to learn this instead of just reading a thread and forgetting everything tomorrow:
BEGINNER:
• Khan Academy Physics
• OpenStax Physics
• The Feynman Lectures
MORE SERIOUS:
• MIT OpenCourseWare
• Walter Lewin's physics lectures
• University-level mechanics textbooks
ADVANCED:
• Classical Mechanics
• Electrodynamics
• Quantum Mechanics
• Statistical Mechanics
• General Relativity
• Quantum Field Theory
Don't try to jump straight into quantum field theory because you watched three n****r in Youyube explain black holes.
Learn the math first.
algebra --> trigonometry --> calculus --> linear algebra --> differential equations
and yeah thats it, this took me around 2-3 days so if you wouldn't mind could u pls rep it and uh id bump it when ever u see it. have a nice day!
From Newton to Quantum Mechanics
INTRO
alr n*****s, this is the best GUIDE u will ever see in any forum
You don't need to be some 333 IQ mathematician to understand the basic ideas. Most of physics is basically:
observe something --> find a pattern --> describe it with math --> test whether it actually works.
I'm going from the absolute basics into some of the more insane shit like relativity, quantum mechanics, black holes and particle physics.
this took me a shit ton of time so PLS REP IT NIGGERRR
- WHAT IS PHYSICS?
Physics is the study of matter, energy, space, time, and the interactions between them.
Pretty much everything physical falls somewhere inside it.
Motion?
Physics.
Light?
Physics.
Electricity?
Physics.
Stars?
Physics.
Why your phone works?
Physics.
Why the universe behaves the way it does?
Also physics.
Some major areas of physics include:
• Classical mechanics
• Electromagnetism
• Thermodynamics
• Optics
• Relativity
• Quantum mechanics
• Nuclear physics
• Particle physics
• Astrophysics
• Cosmology
The funny thing is that these aren't completely separate subjects.
They overlap constantly.
2. UNITS & MEASUREMENT
Before doing physics, you need to be able to describe quantities.
The standard system is SI units.
Length → meter (m)
Time → second (s)
Mass → kilogram (kg)
Temperature → kelvin (K)
Electric current → ampere (A)
From these, we construct other units.
Velocity → m/s
Acceleration → m/s²
Force → newton (N)
1 N = 1 kg·m/s²
Units are actually extremely useful because they can catch mathematical mistakes.
If you're calculating a velocity and somehow end up with kg/s, you've probably fucked something up.
3. SCALARS VS VECTORS
A scalar only has magnitude.
Examples:
• mass
• temperature
• energy
• time
• speed
A vector has magnitude AND direction.
Examples:
• velocity
• acceleration
• force
• displacement
• momentum
For example:
60 km/h
is a speed.
60 km/h north
is a velocity.
Same magnitude, but velocity also tells you the direction.
4. KINEMATICS
Kinematics describes motion without worrying about what causes the motion.
The basic quantities are:
position
velocity
acceleration
Velocity describes how quickly position changes.
v = Δx / Δt
where:
v = velocity
Δx = change in position
Δt = change in time
So if something travels 100 meters in 5 seconds:
v = 100 / 5
v = 20 m/s
simple.
5. ACCELERATION
Acceleration is the change in velocity over time.
a = Δv / Δt
If a car goes from:
0 m/s --> 20 m/s
in 5 seconds:
a = 20 / 5
a = 4 m/s²
That means its velocity increases by about 4 m/s every second.
Acceleration doesn't necessarily mean "speeding up."
An object can accelerate while slowing down or changing direction.
6. NEWTON'S LAWS
Now we get into the GOAT of classical mechanics.
Sir Isaac Newton.
NEWTON'S FIRST LAW
An object remains at rest or continues moving at constant velocity unless acted upon by a net external force.
Basically:
objects don't randomly change their motion.
A stationary object stays stationary.
A moving object keeps moving at constant velocity.
Something has to interact with it to change that.
This is called inertia.
NEWTON'S SECOND LAW
The famous one:
F = ma
Force equals mass times acceleration.
This tells you how force, mass and acceleration are related.
More force --> more acceleration.
More mass -->less acceleration for the same force.
Example:
A 10 kg object experiences a 20 N net force.
a = F / m
a = 20 / 10
a = 2 m/s²
NEWTON'S THIRD LAW
For every action, there is an equal and opposite reaction.
If you push a wall, you exert a force on the wall.
The wall exerts an equal and opposite force on you.
If you jump, you push the Earth downward.
The Earth pushes you upward.
The Earth is obviously so massive that its acceleration is basically negligible compared with yours.
7. GRAVITY
Near Earth's surface, objects accelerate downward at approximately:
g = 9.81 m/s²
Ignoring air resistance, a dropped object accelerates at roughly this rate.
After 1 second:
9.8 m/s
After 2 seconds:
19.6 m/s
After 3 seconds:
29.4 m/s
etc.
The important thing is that mass doesn't determine the acceleration of a freely fallingobject near Earth's surface.
A 1 kg object and a 10 kg object fall at approximately the same acceleration in vacuum.
Air resistance is why things like feathers don't behave the same way in Earth's atmosphere.
8. UNIVERSAL GRAVITATION
Newton didn't stop at Earth's gravity.
He proposed:
F = G(m₁m₂ / r²)
where:
G = gravitational constant
m₁ and m₂ = masses
r = distance between their centers of mass
This tells us that gravitational force:
increases with mass
and decreases with the square of distance.
Double the distance:
1/4 the gravitational force.
Triple the distance:
1/9 the force.
This equation worked insanely well for centuries.
Then Einstein came along.
9. WORK
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In physics, work has a very specific meaning.
Work occurs when a force causes displacement.
W = Fd cosθ
where:
W = work
F = force
d = displacement
θ = angle between the force and displacement
If you push a box forward, you're doing work on it.
If you're holding a heavy object completely stationary, you're exerting force but doing zero mechanical work on the object because it isn't moving.
Physics definitions can be annoying like that.
10. ENERGY
Energy is one of the most important concepts in physics.
There are many forms:
• kinetic energy
• gravitational potential energy
• thermal energy
• chemical energy
• electrical energy
• nuclear energy
• electromagnetic energy
Energy can be transferred and transformed.
But the total energy of an isolated system is conserved.
This is the law of conservation of energy.
11. KINETIC ENERGY
The energy associated with motion:
KE = ½mv²
Notice the velocity is squared.
That means doubling velocity gives four times the kinetic energy.
A 2× increase in velocity:
2² = 4
so:
4× kinetic energy.
This is one reason why increasing speed dramatically increases the energy involved in collisions.
12. POTENTIAL ENERGY
Potential energy is stored energy associated with a system's configuration.
Near Earth's surface:
PE = mgh
where:
m = mass
g = gravitational acceleration
h = height
Raise something higher:
more gravitational potential energy.
Drop it:
that energy can become kinetic energy.
This is basically energy constantly changing forms.
13. MOMENTUM
Momentum is:
p = mv
Mass × velocity.
Momentum is conserved in isolated systems.
This becomes extremely important when studying collisions.
A massive truck moving slowly can have enormous momentum.
A tiny object moving extremely fast can also have significant momentum.
Momentum isn't the same thing as kinetic energy either.
They're related, but different quantities.
14. COLLISIONS
There are different types of collisions.
ELASTIC COLLISION
Momentum is conserved.
Kinetic energy is also conserved.
INELASTIC COLLISION
Momentum is conserved.
Kinetic energy isn't necessarily conserved as kinetic energy.
Some becomes:
• heat
• sound
• deformation
• other forms of energy
A completely inelastic collision is when objects stick together after colliding.
15. CIRCULAR MOTION
An object moving in a circle is accelerating even if its speed stays constant.
Why?
Because velocity includes direction.
The direction is continuously changing.
The inward acceleration is called centripetal acceleration:
a = v² / r
where:
v = speed
r = radius
The corresponding force is:
F = mv² / r
Important:
centripetal force isn't a new fundamental force.
It's simply the name for whatever net force is pointing toward the center of the circular path.
Gravity can provide centripetal force.
Tension can.
Friction can.
etc.
16. ROTATIONAL PHYSICS
Things don't just move linearly.
They can rotate.
Rotational physics has analogues to ordinary mechanics.
Linear:
F = ma
Rotational:
τ = Iα
where:
τ = torque
I = moment of inertia
α = angular acceleration
Torque is basically the rotational equivalent of force.
Push a door near its hinge:
not very effective.
Push it near the handle:
much easier.
Same basic force, different torque.
17. WAVES/
A wave is a disturbance that transfers energy.
Waves can be:
• mechanical
• electromagnetic
Mechanical waves require a medium.
Sound is an example.
Electromagnetic waves don't require a material medium.
Light is an example.
Important wave quantities:
wavelength (λ)
frequency (f)
amplitude
speed (v)
And:
v = fλ
Higher frequency with the same wave speed means shorter wavelength.
18. SOUND
Sound is a mechanical wave.
In air, it's generally a longitudinal pressure wave.
The particles oscillate roughly parallel to the direction the wave travels.
Frequency determines the perceived pitch.
Higher frequency -->higher pitch.
Amplitude is related to the intensity of the sound.
Speed of sound depends on the medium and its properties.
In air at ordinary conditions it's roughly:
343 m/s
but it changes with temperature and other factors.
19. LIGHT
Light is electromagnetic radiation.
The electromagnetic spectrum includes:
• radio
• microwave
• infrared
• visible light
• ultraviolet
• X-rays
• gamma rays
They're all electromagnetic waves.
The main difference is frequency and wavelength.
Visible light is only a tiny portion of the electromagnetic spectrum.
20. ELECTRICITY
Electric charge comes in positive and negative forms.
Like charges repel.
Opposite charges attract.
The SI unit of charge is the coulomb (C).
Electric current measures the rate of charge flow:
I = Q / t
where:
I = current
Q = charge
t = time
Current is measured in amperes.
21. VOLTAGE
Voltage is electric potential difference.
A useful analogy is pressure in a fluid system.
It's not perfect, but it helps.
Voltage provides the potential difference that can drive current through a circuit.
One of the most famous equations:
V = IR
Ohm's law.
V = voltage
I = current
R = resistance
Increase voltage while resistance stays constant:
current increases.
Increase resistance while voltage stays constant:
current decreases.
22. ELECTROMAGNETISM
Electricity and magnetism aren't actually completely separate forces.
They're aspects of one electromagnetic interaction.
Moving charges produce magnetic fields.
Changing magnetic fields can produce electric fields.
This connection is described by Maxwell's equations.
Maxwell's work was absolutely massive for physics.
It showed that electromagnetic waves exist and that light itself is electromagnetic radiation.
23. THERMODYNAMICS
Thermodynamics studies heat, temperature, energy and entropy.
THE ZEROTH LAW
If A is in thermal equilibrium with B, and B with C, then A and C are in thermal equilibrium.
Basically:
temperature is transitive.
THE FIRST LAW
Energy is conserved.
A common form is:
ΔU = Q - W
depending on the sign convention being used.
Internal energy can change through heat transfer and work.
THE SECOND LAW
Entropy of an isolated system tends to increase.
This gives us the direction of many physical processes.
Heat naturally flows from hotter objects toward colder objects.
You don't normally see a cold drink spontaneously becoming colder while heating the room.
THE THIRD LAW
As a system approaches absolute zero, its entropy approaches a minimum under appropriate conditions.
Absolute zero:
0 K
approximately:
−273.15°C
24. ENTROPY
Entropy gets explained badly online all the time.
It's not simply:
"disorder."
That's a useful beginner analogy, but incomplete.
More fundamentally, entropy is related to the number of microscopic configurations consistent with a macroscopic state.
Boltzmann gave us:
S = k ln Ω
where:
S = entropy
k = Boltzmann constant
Ω = number of accessible microstates
This is where thermodynamics starts connecting with statistical mechanics.
25. SPECIAL RELATIVITY
Now we're leaving Newton behind.
Einstein's special relativity is based on two major ideas:
- The laws of physics are the same in all inertial reference frames.
- The speed of light in vacuum is the same for all inertial observers.
Time isn't universal.
Distances aren't universal.
Simultaneity isn't universal.
They're dependent on the observer's state of motion.
26. TIME DILATION
A moving clock is observed to run slower relative to a given inertial frame.
The Lorentz factor is:
γ = 1 / √(1 − v²/c²)
As velocity v approaches the speed of light c, γ becomes very large.
You can't accelerate a massive object to the speed of light.
The energy required approaches infinity in special relativity.
So:
massive objects cannot reach c.
Light doesn't have this problem because photons are massless.
27. LENGTH CONTRACTION
Objects moving relative to an observer are measured to be shorter along their direction of motion.
The relationship is:
L = L₀ / γ
where:
L₀ = proper length
Again:
this isn't simply an optical illusion.
It's a consequence of spacetime geometry.
28. MASS–ENERGY EQUIVALENCE
The famous equation:
E = mc²
(if u really reading this PM me and ill teach u other cool shit)
means mass is associated with energy.
Even a tiny amount of mass corresponds to a huge amount of energy because c² is enormous.
This relationship is fundamental to nuclear physics.
29. GENERAL RELATIVITY
Special relativity deals with inertial frames and high speeds.
General relativity brings gravity into the picture.
Einstein's big idea:
gravity isn't simply a conventional force.
Mass and energy curve spacetime.
Objects then move through that curved spacetime.
A common analogy is a heavy ball deforming a rubber sheet.
It's useful, but imperfect because actual spacetime has four dimensions and isn't literally a rubber sheet.
The basic idea:
matter tells spacetime how to curve,
and curved spacetime tells matter how to move.
30. BLACK HOLES (for the black holes I asked ai to give me info so I could read it and put what I understood here)
If enough mass is compressed into a sufficiently small region, you can form a black hole.
The boundary surrounding it is called the event horizon.
Once something crosses the event horizon, it cannot send information back out to distant observers through ordinary causal paths.
Black holes aren't cosmic vacuum cleaners.
If the Sun were somehow replaced by a black hole of exactly the same mass, Earth's orbit would initially remain essentially the same.
We'd have a much bigger problem because we'd lose sunlight.
31. QUANTUM MECHANICS
Now we get into the part where classical intuition starts getting absolutely destroyed.
Quantum mechanics describes nature at microscopic scales.
Atoms.
Electrons.
Photons.
Quarks.
etc.
Some quantities come in discrete amounts.
Particles can behave like waves.
Waves can behave like particles.
And measurement plays a fundamental role in quantum theory.
32. WAVE-PARTICLE DUALITY
Electrons aren't simply tiny classical balls.
They can produce interference patterns like waves.
Photons also exhibit both particle-like and wave-like behavior.
The famous double-slit experiment demonstrates this beautifully.
Send particles through two slits.
Even when particles are sent one at a time, the accumulated results can form an interference pattern.
That's fucking weird.
And it's real.
33. THE UNCERTAINTY PRINCIPLE
Heisenberg's uncertainty principle is commonly written:
ΔxΔp ≥ ħ/2
You cannot simultaneously know position and momentum with arbitrary precision.
This isn't simply a limitation caused by bad measuring equipment.
It's built into quantum mechanics itself.
The more precisely certain pairs of quantities are defined, the less precisely the corresponding conjugate quantity can be defined.
34. QUANTUM SUPERPOSITION
A quantum system can exist in a superposition of possible states.
Before measurement, its quantum state can contain multiple possible outcomes.
This doesn't simply mean:
"the particle is literally doing every classical thing at once."
Quantum mechanics describes the system using a state that contains amplitudes for possible measurement outcomes.
The mathematical formalism is weird.
But it works.
Insanely well.
35. QUANTUM ENTANGLEMENT
Two quantum systems can become entangled so that their measurement outcomes are correlated in ways that cannot be explained by ordinary classical hidden variables.
Measure one and you gain information about the other.
Einstein famously disliked the implications and referred to it as:
"spooky action at a distance."
Important though:
entanglement does NOT let you send usable information faster than light.
No FTL Discord messaging unfortunately.
36. THE STANDARD MODEL
Particle physics describes the known elementary particles and their interactions through the Standard Model.
MATTER PARTICLES
QUARKS:
• up
• down
• charm
• strange
• top
• bottom
LEPTONS:
• electron
• muon
• tau
• electron neutrino
• muon neutrino
• tau neutrino
FORCE-CARRYING PARTICLES:
• photon
• gluons
• W bosons
• Z boson
and the:
Higgs boson
The Standard Model is one of the most successful scientific theories ever created.
But it isn't a complete theory of everything.
37. THE HIGGS BOSON
The Higgs field exists throughout space.
Elementary particles interact with this field to different degrees.
The Higgs boson is an excitation of that field.
It was experimentally discovered at CERN in 2012.
And no:
the Higgs boson does not give literally everything mass.
For example, most of the mass of ordinary protons and neutrons comes from the energy associated with the strong interaction inside them, rather than directly from the Higgs mechanism.
38. NUCLEAR PHYSICS (AI helped me understand this shit cuz Im bad at nuclear physics sorry)
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Atomic nuclei contain:
protons + neutrons
These are collectively called nucleons.
There are two major nuclear processes worth knowing:
FISSION
A heavy nucleus splits into smaller nuclei.
This can release energy.
FUSION
Light nuclei combine into heavier nuclei.
This can also release enormous amounts of energy.
The Sun is powered by nuclear fusion.
39. ANTIMATTER
Most matter particles have corresponding antiparticles.
For example:
electron → positron
proton → antiproton
When matter and antimatter particles meet, they can annihilate into other forms of energy and particles while conserving the relevant quantities.
Why there is so much more matter than antimatter in our observable universe is still a major question in physics.
40. DARK MATTER
We have strong evidence that there is more gravitationally interacting matter in the universe than the matter we can see directly.
Galaxies rotate in ways that don't match the amount of visible matter alone.
Gravitational lensing also provides evidence.
Something appears to be contributing additional gravitational effects.
We call the unknown component:
dark matter.
We know a lot about what it does gravitationally.
We still don't know exactly what it is.
41. DARK ENERGY
The expansion of the universe is accelerating.
Whatever is responsible for this accelerated expansion is commonly called:
dark energy.
We don't currently have a complete understanding of its fundamental nature.
The simplest explanation is a cosmological constant associated with vacuum energy.
But this is still an active area of research.
42. THE UNIVERSE
The observable universe is big af
Galaxies.
Stars.
Planets.
Nebulae.
Black holes.
Dark matter.
And probably a whole lot of shit we haven't discovered yet.
The universe is expanding.
This doesn't mean galaxies are simply flying through pre-existing empty space from one central explosion.
On sufficiently large scales, space itself is expanding.
The Big Bang model describes the early hot, dense state of our observable universe and its subsequent expansion.
It doesn't necessarily answer the philosophical question:
"what happened before the Big Bang?"
idk n****r im not God so I cant say
43. WHY PHYSICS IS SO FUCKING INTERESTING TO ME
The crazy thing about physics is how much can come from a relatively small number of principles.
Newtonian mechanics explains an enormous range of everyday motion.
Maxwell's equations unify electricity and magnetism.
Thermodynamics explains heat and energy transfer.
Relativity changes our understanding of space and time.
Quantum mechanics describes the microscopic world.
And modern physics is still incomplete.
We don't yet have a fully accepted quantum theory of gravity.
We don't know exactly what dark matter is.
We don't know the fundamental nature of dark energy.
We don't completely understand why the observable universe contains vastly more matter than antimatter.
There is still an insane amount left to figure out.
44. FINAL TL;DR
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Physics starts with some pretty simple ideas:
motion
forces
energy
momentum
waves
electricity & magnetism
thermodynamics
relativity
quantum mechanics
particle physics
cosmology
if u get really interested in ts u willl most likely start asking ur self:
What is space?
What is time?
Why does gravity exist?
What is dark matter?
Why is there something rather than nothing?
That's basically why physics is so fucking cool.
You start with:
F = ma
and somehow end up talking about curved spacetime, quantum fields and the origin of the universe.
RESOURCES
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If you actually want to learn this instead of just reading a thread and forgetting everything tomorrow:
BEGINNER:
• Khan Academy Physics
• OpenStax Physics
• The Feynman Lectures
MORE SERIOUS:
• MIT OpenCourseWare
• Walter Lewin's physics lectures
• University-level mechanics textbooks
ADVANCED:
• Classical Mechanics
• Electrodynamics
• Quantum Mechanics
• Statistical Mechanics
• General Relativity
• Quantum Field Theory
Don't try to jump straight into quantum field theory because you watched three n****r in Youyube explain black holes.
Learn the math first.
algebra --> trigonometry --> calculus --> linear algebra --> differential equations
and yeah thats it, this took me around 2-3 days so if you wouldn't mind could u pls rep it and uh id bump it when ever u see it. have a nice day!
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Not sure who the target audience is though
i had a lecture on it last week and its frying my brain