Key Concepts in Physics

Gravitational Force: Attraction between masses; governs planetary motion.
Electromagnetic Force: Interaction between charged particles; responsible for electricity and magnetism.
Weak Nuclear Force: Responsible for radioactive decay; plays a role in nuclear reactions.
Strong Nuclear Force: Binds protons and neutrons in the nucleus; strongest force at short distances.

Distance vs. Displacement:
- Distance: Total path length traveled.
- Displacement: Change in position; vector quantity.
Speed vs. Velocity:
- Speed: Scalar quantity (magnitude only).
- Velocity: Vector quantity (magnitude and direction).
Acceleration: Rate of change of velocity; can be positive or negative (deceleration).

First Law (Inertia): An object will remain at rest or in uniform motion unless acted upon by an external force.
Second Law: Force equals mass times acceleration (F = ma).
Third Law: For every action, there is an equal and opposite reaction.

Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Conservation of Momentum: Total momentum in a closed system remains constant.

Zeroth Law: If A is in thermal equilibrium with B, and B with C, then A is in equilibrium with C.
First Law: Energy is conserved; heat added to a system equals work done by the system plus change in internal energy.
Second Law: Entropy of an isolated system always increases; heat cannot spontaneously flow from cold to hot.
Third Law: As temperature approaches absolute zero, entropy approaches a minimum.

Wave Properties: Frequency, wavelength, amplitude, speed.
Types of Waves:
- Transverse Waves: Particles move perpendicular to wave direction.
- Longitudinal Waves: Particles move parallel to wave direction (e.g., sound waves).
Sound: Mechanical wave requiring a medium; travels fastest in solids.

Reflection: Bouncing of light off surfaces; angle of incidence equals angle of reflection.
Refraction: Bending of light as it passes through different media.
Total Internal Reflection: Complete reflection of light within a medium; occurs at angles greater than the critical angle.

Theory of Relativity: Introduced by Einstein; describes how measurements of space and time vary for observers in different frames of reference.
Quantum Mechanics: Study of particles at atomic and subatomic levels; incorporates principles of uncertainty and wave-particle duality.

SI Units: Standard units include meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd).
Common Derived Units:
- Force: Newton (N)
- Energy: Joule (J)
- Power: Watt (W)

These notes cover essential aspects of physics, emphasizing fundamental concepts, laws, and principles.

Gravitational Force: Attracts objects with mass, governing planetary motion and the structure of the universe.
Electromagnetic Force: Governs interactions between charged particles. Responsible for electricity, magnetism, and chemical bonding.
Weak Nuclear Force: Responsible for radioactive decay and plays a crucial role in nuclear reactions.
Strong Nuclear Force: The strongest force at short distances, binding protons and neutrons together in the nucleus of atoms.

Distance is the total path length traveled.
Displacement is the change in position from the starting point, a vector quantity indicating both magnitude and direction.
Speed is a scalar quantity, measuring how fast an object is moving.
Velocity is a vector quantity, indicating both the speed and the direction of motion.
Acceleration is the rate of change of velocity, indicating how quickly the velocity is changing.

First Law (Inertia): Objects at rest tend to stay at rest, and objects in motion tend to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Second Law: The net force acting on an object is equal to its mass multiplied by its acceleration (F = ma).
Third Law: For every action, there is an equal and opposite reaction.

Work is done when a force causes displacement. It is calculated by multiplying the force, the displacement, and the cosine of the angle between them (W = F * d * cos(θ)).
Kinetic Energy (KE) is the energy of motion. It is calculated as half the mass multiplied by the velocity squared (KE = 1/2 mv²).
Potential Energy (PE) is stored energy due to an object's position. It is often associated with gravitational potential energy (PE = mgh), where m is mass, g is gravitational acceleration, and h is height.

Conservation of Energy: Energy cannot be created or destroyed, only transformed from one form to another.
Conservation of Momentum: Total momentum in a closed system remains constant. Momentum is the product of an object's mass and its velocity.

Zeroth Law of Thermodynamics: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
First Law of Thermodynamics: Energy is conserved in thermodynamic processes. The total energy of a closed system remains constant, although it can be converted between different forms, such as heat, work, and internal energy.
Second Law of Thermodynamics: Entropy, a measure of disorder, always increases in isolated systems over time. Heat cannot spontaneously flow from a cooler body to a hotter body.
Third Law of Thermodynamics: As the absolute temperature of a system approaches zero, the entropy of the system approaches a minimum value. It is impossible to reach absolute zero.

Wave Properties: Key features of waves include their frequency, wavelength, amplitude, and speed.
Transverse Waves: Particles oscillate perpendicular to the direction of wave propagation (e.g., light waves).
Longitudinal Waves: Particles oscillate parallel to the direction of wave propagation (e.g., sound waves).
Sound: A mechanical wave requiring a medium to travel. Sound travels fastest in solids, then liquids, and slowest in gases.

Reflection: The bouncing of light off a surface. The angle of incidence (angle of incoming light) equals the angle of reflection (angle of outgoing light).
Refraction: The bending of light as it passes from one medium to another, due to changes in the speed of light.
Total Internal Reflection: When light traveling in a denser medium strikes the boundary with a less dense medium at an angle greater than the critical angle, it is completely reflected back into the denser medium.

Theory of Relativity: Developed by Albert Einstein, it describes how measurements of space and time are relative, depending on the observer's frame of reference. It includes the concepts of special relativity and general relativity.
Quantum Mechanics: Studies the behavior of matter and energy at the atomic and subatomic levels. Key principles include the quantization of energy, wave-particle duality, and the uncertainty principle.

SI Units (International System of Units): The standard system of units used in science and engineering.
Commonly Used SI Units:
- Length: meter (m)
- Mass: kilogram (kg)
- Time: second (s)
- Current: ampere (A)
- Temperature: kelvin (K)
- Amount of Substance: mole (mol)
- Luminous Intensity: candela (cd)
Derived Units:
- Force: Newton (N) (1 N = 1 kg * m/s²)
- Energy: Joule (J) (1 J = 1 N * m)
- Power: Watt (W) (1 W = 1 J/s)