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

Modern Physics

This branch of physics considers the theory of relativity and quantum theory in describing microscopic systems like atoms.

Model of Modern Physics

In the late nineteenth century, it was a common belief that all phenomena of nature could be described by Newton's laws, principles of thermodynamics, and the laws of electromagnetism, which were based on a mechanical conception of the universe.

Reaffirmation of Modern Physics

In 1905, Albert Einstein produced a series of works that revolutionized physics, mainly due to the wave-particle duality of light and the theory of relativity, among others.

Classification of Modern Physics

It is generally known to study phenomena that occur at the speed of light or values close to it, or whose spatial... Continue reading "Modern Physics: Relativity, Quantum Mechanics, and Nuclear Processes" »

Force Interactions

Strength: Action of one body on another, or interaction. Net force (resultant) is the vector sum of all forces acting simultaneously on the same body.

Like acceleration and speed, force is a vector quantity, defined by its magnitude and direction.

Force Measurement

To combine forces on a body, add them vectorially. The net force is equivalent to a single force producing the same effect.

Special Forces

Weight

Weight is the gravitational force a planet or star exerts on a body.

Normal Force

The normal force is a contact force preventing an object from passing through a surface, always perpendicular to it.

Friction Force

Friction force is exerted between two surfaces in contact. Its magnitude on solids depends on surface roughness.

F_r =

Forces and Motion

An outside influence that changes a body's state of rest or motion is called force.

Types of Forces

Normal Force: The force perpendicular to a surface exerted on a body by that surface.

Friction: A force resulting from physical contact between a body and its surroundings, opposing motion.

Gravity: A force proportional to acceleration, attracting objects with mass towards each other.

Fundamental Forces: Gravity, Electromagnetic, Strong Nuclear, and Weak Nuclear.

Newton's Third Law

Also known as the Law of Action and Reaction.

Inertial Reference Frame

A frame where a body moves with constant speed if no force acts on it.

Work and Momentum

Work

A scalar quantity obtained from the product of force and displacement.

Momentum

Define this formula:... Continue reading "Physics Fundamentals: Forces, Motion, and Vectors" »

Physics and Chemistry

The scientific method is the process used to investigate natural phenomena. It involves observation, research, hypothesis formulation, experimentation, result interpretation, law formulation, theory and model development, and finally, a scientific report.

Magnitude: A measurable quantity. A crucial magnitude is defined independently; a derived magnitude is defined from other key magnitudes.

Measurement: Comparing a quantity with a unit. The result is often expressed numerically.

Unit: A standard quantity used for comparison. Units must be constant, universal, and reproducible. The International System of Units (SI) is an agreed-upon system.

Accuracy: The smallest variation a tool can measure.

Substance: Anything that has... Continue reading "Physics and Chemistry Fundamentals" »

Scientific Theory: A set of principles and laws capable of explaining a particular aspect of nature.

Physical Property: Any observable property of bodies which could be objectively quantified by a measurement process.

Physical Unit: Any arbitrary amount of a magnitude that is adopted by agreement as a pattern to that magnitude.

Types of Magnitudes

Extensive and intensive, scalar and vector.

• Intensive: All quantities whose numerical value does not depend on the size of the body being studied. Those that depend on the value of body size are extensive.

Scalar Quantities

Those that are completely defined by a numerical value and its corresponding unit.

Vector Quantities

Are those for which, besides the numerical value and the appropriate unit, you need... Continue reading "Understanding Scientific and Physical Concepts" »

Balance

A body is in equilibrium when at rest or when moving with uniform rectilinear motion. Some conditions are:

• When a body acts on a single force, it cannot be in balance.
• Two equal and opposite forces acting on a body produce equilibrium.
• The total strength of various forces must be zero for a body to be in balance.

Resultant Force

The resultant force (R) is the force that substitutes various forces, and its effect is the same as all the initial forces together. The calculation of the force resulting from a group of them acting on a body is called the composition of forces.

Resultant Force of Forces Applied in the Same Direction and Sense

• The point of application, direction, and sense will be the same as those of the component forces.
• The module

Viscous friction forces cause the fluid layers in direct contact with a solid surface to adhere to it, resulting in no relative motion. Additionally, there cannot be any relative motion between the fluid and the wall perpendicular to the surface. Therefore, the boundary condition for a solid wall is:

(Wall-fluid relative velocity). For an ideal fluid without frictional forces, the condition is:

The force acting on a solid wall can be expressed as:

The force per unit area is then:

This represents the normal force to the surface (outgoing and incoming fluid at the solid). The first term represents static pressure, and the second term represents the viscous friction force acting on the surface. For a surface separating two immiscible fluids, the... Continue reading "Fluid Mechanics: Boundary Conditions and Dimensional Analysis" »

How is Sound Produced? Through Vibration and Resonance

Vibrations: Sound is produced as a result of the vibration of a medium or object. Sound always occurs because of a vibration.

Resonance: Frequencies are called natural or characteristic frequencies of vibration that are exhibited when they are left swinging or vibrating. Resonance occurs when the system is forced periodically with a frequency (rhythm) that coincides with some of its natural frequencies. This increases energy.

Vibrational Motion: The motion made by a body occupying symmetrical positions successively to a position of equilibrium.

Fundamental Concepts of Motion

• Vibration: The path of a moving body in vibration from passing through a point in its path until it returns to the same

Motion in Physics

Introduction to Motion

Kinematics is the branch of physics that studies movement. Objects can be in two states: at rest or in motion. An object is in motion when it changes its position over time relative to a fixed reference point. A reference system is something assumed to be at rest, against which movements are described. It's crucial to use a reference system when studying the motion of an object.

Understanding Rest

A body is at rest when its position doesn't change over time relative to other objects we consider stationary. To study movement, we need to know:

• Position: The body's location in space relative to a reference system.
• Trajectory: The line describing the body's movement (straight or curved).
• Distance: The length covered

Henry's Experiment

If a driver or wire moves perpendicular to a magnetic field, it causes a potential difference across the ends of the conductor. This potential difference causes a current if the driver is part of a closed circuit.

Faraday's Law

Any change in magnetic flux through a circuit causes an induced current. This is produced by a known electromotive force (induced EMF), which exists only for the duration of this change in flux and is proportional to the rate of change of flow.

Lenz's Law

The direction of the induced current is such that it opposes the cause that produces it.

Alternator

An alternator consists of a flat coil of N turns, rotating with constant angular velocity within a uniform magnetic field B. In the coil, an EMF is induced... Continue reading "Electromagnetism and Optics: Principles and Applications" »