Key Concepts in Physics

Fundamental Forces
- Gravitational Force: Attraction between masses.
- Electromagnetic Force: Interaction between charged particles.
- Weak Nuclear Force: Responsible for radioactive decay.
- Strong Nuclear Force: Holds protons and neutrons in the nucleus.
Laws of Motion (Newton's Laws)
1. First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.
2. Second Law (F=ma): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
3. Third Law: For every action, there is an equal and opposite reaction.
Work, Energy, and Power
- Work: Energy transferred by a force acting over a distance (W = F × d × cos(θ)).
- Kinetic Energy (KE): Energy of motion (KE = 1/2 mv²).
- Potential Energy (PE): Energy stored in an object due to its position (PE = mgh).
- Power: Rate of doing work or transferring energy (P = W/t).
Thermodynamics
- First Law: Energy cannot be created or destroyed, only transformed (ΔU = Q - W).
- Second Law: Entropy of an isolated system always increases; heat cannot spontaneously flow from cold to hot.
- Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Wave Properties
- Amplitude: Maximum displacement of points on a wave.
- Frequency (f): Number of cycles per second (Hz).
- Wavelength (λ): Distance between successive crests or troughs.
- Speed of a Wave: v = f × λ.
Electromagnetism
- Electric Charge: Fundamental property of matter; exists in positive and negative forms.
- Ohm's Law: V = IR (Voltage = Current × Resistance).
- Electromagnetic Wave: Waves that carry electromagnetic energy (e.g., light).
Classical Mechanics vs. Quantum Mechanics
- Classical Mechanics: Deals with macroscopic objects and motions (Newtonian physics).
- Quantum Mechanics: Explains the behavior of particles at atomic and subatomic levels.
Relativity
- Special Relativity: Postulates that the laws of physics are the same for all non-accelerating observers and that the speed of light is constant.
- General Relativity: Theory of gravitation describing gravity as a curvature of spacetime caused by mass.

Important Principles

Conservation Laws: Energy, momentum, and charge are conserved in isolated systems.
Projectile Motion: Motion of an object thrown into the air, affected by gravity, characterized by parabolic paths.
Circular Motion: Motion along a circular path, characterized by centripetal force acting towards the center of the circle.

Applications of Physics

Engineering: Design of structures, machines, and systems.
Astronomy: Understanding celestial bodies and phenomena.
Medical Physics: Application of physics concepts in medicine, such as imaging and radiation therapy.

Problem-Solving Techniques

Identify known and unknown variables.
Diagram the problem (if applicable).
Apply relevant physics equations.
Perform unit conversions if necessary.
Check the reasonableness of results.

Fundamental Forces

Gravitational Force: Attraction between any two objects with mass. The force is weaker but acts over long distances.
Electromagnetic Force: Interaction between charged particles, responsible for electricity, magnetism, and light.
Weak Nuclear Force: Responsible for radioactive decay, acting within atomic nuclei.
Strong Nuclear Force: Holds protons and neutrons together within the nucleus, overcoming electrostatic repulsion between protons.

Laws of Motion (Newton’s Laws)

First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion at a constant velocity unless acted upon by a net external force.
Second Law (F=ma): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
Third Law: For every action, there is an equal and opposite reaction. This means that forces always come in pairs, acting on different objects.

Work, Energy, and Power

Work: Energy transferred by a force acting over a distance.
Kinetic Energy: Energy of motion, dependent on mass and velocity.
Potential Energy: Energy stored in an object due to its position or configuration.
Power: The rate at which work is done or energy is transferred.

Thermodynamics

First Law: Energy cannot be created or destroyed, only transformed from one form to another.
Second Law: Entropy (disorder) of an isolated system always increases. This means heat flows spontaneously from hot to cold.
Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Wave Properties

Amplitude: The maximum displacement of points on a wave from their equilibrium position.
Frequency: Number of cycles or oscillations of the wave per second.
Wavelength: The distance between two successive crests or troughs of a wave.
Speed of a Wave: Determined by the product of its frequency and wavelength.

Electromagnetism

Electric Charge: A fundamental property of matter, existing in positive and negative forms.
Ohm’s Law: Relates voltage (V), current (I), and resistance (R) in a circuit.
Electromagnetic Wave: Waves that carry electromagnetic energy, including light, radio waves, and X-rays.

Classical Mechanics vs. Quantum Mechanics

Classical Mechanics: Deals with macroscopic objects and their motion, governed by Newton’s laws.
Quantum Mechanics: Explains the behavior of particles at atomic and subatomic levels, featuring wave-particle duality and quantized energy levels.

Relativity

Special Relativity: Deals with the relationship between space and time, based on the fundamental postulates that the laws of physics are the same for all inertial observers and the speed of light is constant.
General Relativity: Explains gravity as a curvature of spacetime caused by mass and energy.