Notes, summaries, assignments, exams, and problems for Physics

Energy Definition

It is a property of any body or material system which can be transformed by changing its position or state, as well as act on them, originating from other processes of transformation.

Forms of Energy

• Kinetic Energy: Energy possessed by a moving body.
• Potential Energy: Associated with the position of a body relative to a reference point (e.g., the floor).
• Thermal Energy: Due to the vibratory motion of the molecules that constitute matter.
• Radiant Energy: Associated with electromagnetic radiation (such as light or microwaves).
• Nuclear Energy: Associated with the process of fusion (union of nuclei) or fission (rupture of nuclei) that takes place inside atoms.
• Chemical Energy: Associated with chemical reactions (e.g., combustion). This

John Dalton: The First Theory of Matter

John Dalton proposed the first theory of matter.

William Crookes: Perfecting Vacuum Tubes

William Crookes (1832-1919) perfected devices using a glass tube that had undergone a partial vacuum and contained two electrodes, one positive and one negative, connected to a source of high-voltage continuous current.

J.J. Thomson: Discovering the Electron

In 1897, J.J. Thomson proved that the cathode ray consisted of minute particles of negative electric charge that are attracted by the positive electrode. He achieved determining the relationship between charge and mass for these particles. He carefully measured how magnetic and electric fields deviated the electrons' trajectory. Independently of their origin, they... Continue reading "Key Discoveries in Atomic Theory and Radioactivity" »

What is a Wave?

A wave (k) is a perturbation that transports energy, originating from a periodic disturbance. Waves exhibit several key characteristics:

• Frequency: The number of wavelengths or impulses passing a point per unit of time.
• Wavelength: The distance traveled by the wave during one cycle.

Waves extend in all directions. When they encounter an obstacle, they undergo:

• Reflection: A change in direction.
• Refraction: If they enter the obstacle, their speed changes.

Kinds of Mechanical Waves

Waves can be classified based on their origin:

Mechanical Waves

These require a medium to propagate. A sudden pressure change can cause them.

Electromagnetic Waves

These occur due to electrical and magnetic disturbances.

The speed of a wave depends on its nature... Continue reading "Understanding Wave Physics: Characteristics and Interactions" »

Fundamental Concepts of Force and Motion

Force: Every action can change the state of rest or motion of a body, or result in any deformation. Newton: The force that, when applied to a body of mass 1 kg, communicates an acceleration of 1 m/s².

Resultant Force: The vector sum of all forces in the system.

Conditions of Equilibrium

• Translational Equilibrium: For translational motion not to exist, the resultant of the system of forces that acts on the body should be null.
• Rotational Equilibrium: For rotational movement not to exist, the resultant moment of the system of forces that acts on the body must be zero.

Universal Gravitation and Electric Fields

Universal Law of Gravitation: Two material particles attract each other with a force proportional to... Continue reading "Fundamental Principles of Classical Physics and Dynamics" »

Wave Motion

Wave motion refers to the transmission of a disturbance from one point to another without the net transport of matter.

Wave Classification

Based on Direction of Propagation

• One-dimensional waves: Propagate in a single direction.
• Two-dimensional waves: Propagate in two directions.
• Three-dimensional waves: Propagate in three directions.

Based on Medium of Propagation

• Mechanical waves: Require a material medium for propagation. Their speed depends on the characteristics of the medium.
• Electromagnetic waves: Do not require a material medium and can propagate in a vacuum (e.g., visible light).

Based on Direction of Disturbance

• Transverse waves: The direction of propagation is perpendicular to the direction of the disturbance.
• Longitudinal waves:

Geocentric Theory

Aristotle proposed the following:

• The Earth is round and immobile at the center of a celestial sphere, which houses the stars.
• The planets and stars rotate in a celestial sphere with uniform circular motion around the Earth.

Ptolemy improved Aristotle's theory. The Ptolemaic theory was based on circular orbits but later included eccentric orbits and epicycles to describe the movement of the planets. He maintained that the Earth was the center of the universe.

Heliocentric Theory

Copernicus and Galileo, who demonstrated this theory with a microscope he had built, proposed the heliocentric theory. However, Copernicus did not reveal his theory until the 16th century. It affirmed the following points:

• The Sun is at the center of the

Force is a physical quantity that can cause a body to deform or change its state of motion (start moving, stop, or change direction). As a vector quantity, force has both magnitude and direction. Its magnitude is measured in Newtons (N) within the International System of Units (SI).

Characteristics of a Force

Since force is a vector quantity, to fully define its characteristics, we need to know:

• Application Point: This is the specific point on the body where the force is applied. It represents the origin of the force vector.
• Magnitude (or Intensity): This is the numerical value indicating the strength of the force, measured in Newtons. It corresponds to the length of the force vector.
• Sense: This indicates the specific direction along the line of

Coulomb's Law: The magnitude of each of the electrical forces that interact with two point charges at rest is directly proportional to the product of the magnitude of both charges and inversely proportional to the square of the distance that separates them. Coulomb's law is valid only in stationary conditions, ie when there is movement of charge or, as an approximation when the movement takes place at low speeds and in uniform rectilinear trajectories. That is why it is called electrostatic force.

The magnitude of this force is worth: F = K • Qq / r ²

The value of CTE of proportionality K depends on the chosen system of units and the medium interposed between the load. It is, tannate, a universal constant. If the charges are in vacuum and... Continue reading "Fundamental Concepts of Electrostatics: Coulomb's Law" »

Understanding Triangles and Their Properties

A triangle is a polygon with three sides. It is determined by three line segments called sides or three non-aligned points called vertices.

Key Characteristics of Triangles

• Plane figures: They exist in a two-dimensional plane.
• Area and Volume: They have area but no volume.
• Polygons: Triangles are classified as polygons.
• Interior Angles: The sum of its interior angles always equals 180°.

Classification of Triangles

Classification by Sides

• Equilateral: All three sides measure the same length.
• Isosceles: Two sides measure the same length.
• Scalene: All sides have different lengths.

Classification by Angles

• Right-angled: Contains one right angle (90°).
• Obtuse: One angle is obtuse (greater than 90°) and the other

Fundamental Concepts and Assumptions

Temperature is a physical quantity whose value is an index of the degree of molecular kinetic energy.

Temperature Scales

Temperature scales are based on two fixed points:

• The conventional temperature scale.
• The absolute temperature scale (Kelvin, °K).

First Postulate: Temperature and Thermal Gradient

Temperature is a scalar quantity that, at each point, is a function of its position coordinates and time.

Defining the Thermal Gradient

If we consider a stationary field, we can define the gradient of $T$ at each point as a vector given by the expression:

This vector gives us the thermal gradient at each point of the field.

Statement of the First Postulate

The First Postulate states: "Heat is a form of energy exchange