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

Transformation: na transformació is called a vector x a vector x 'in a way that the correspondence is one to one.
Vector: Vectors are oriented segments with direcció n respect n mod aplicació point or size or module, which can apply various operations.
Consistency: The congruences are transformations that do not change the dimensions of a figure in the background. Such transformations are called isometries movements or in the plane
Translation:He said that figure was applied translational motion if all points of the same description line segments parallel, equal and the same direction. It is called translational plane (or space) to any transformation which makes each point P corresponderun point P 'such that the vector PP' has a LENGTH... Continue reading "Geometric Transformations: Definitions, Isometries, and the Golden Ratio" »

Extrasolar Planets

An extrasolar planet is a planet orbiting a star other than our Sun. There are two general ways of learning about a distant object: directly, which means by obtaining images or spectra of the object, and indirectly, which means by inferring the object’s existence or properties without actually seeing it. There are two major indirect approaches to finding and studying extrasolar planets:

1. Observing the motion of a star to detect the subtle gravitational tugs
2. Observing changes to a star’s brightness that occur when one of its planets passes in front of the star as viewed from Earth.

Planets exert gravitational tugs on their star, causing the star to orbit around the system center of mass. Gravitational tugs: we can detect a... Continue reading "Discovering Extrasolar Planets: Methods and Significance" »

What is Cosmology?

Cosmology Defined

Cosmology is the study of the origin, present structure, evolution, and density of the universe.

The Cosmological Principle

The cosmological principle is the basic assumption that physical laws are true everywhere in the universe, not just on Earth.

The Expanding Universe

Galactic Recession

We observe galaxy clusters receding from us, which implies that the universe is expanding. Galaxies farthest from us are moving away the fastest; the farther the distance, the faster the speed.

Hubble's Law

Hubble's Law states that a galaxy’s velocity of recession (v) is directly proportional to its distance from us (d). The formula is v = Hd.

The Hubble Constant

The Hubble constant (H) is a crucial value that gives the rate at... Continue reading "Cosmology Fundamentals: The Big Bang, Hubble's Law, and the Universe's Fate" »

The Proton-Proton Chain: Powering Low-Mass Stars

The proton-proton chain is the series of nuclear reactions by which low-mass stars, including our Sun, fuse hydrogen into helium. This process is crucial for stellar energy generation.

Gravitational equilibrium and energy balance work together as a natural thermostat, maintaining the Sun’s core temperature and fusion rate at a steady level.

Unraveling the Sun's Energy Source

Early scientific theories proposed that the Sun's energy came from chemical reactions or gravitational collapse. However, these theories were disproven:

• Chemical burning: Ruled out because it cannot account for the Sun’s immense luminosity.
• Gravitational collapse: The conversion of gravitational potential energy into heat as

Introduction

White Dwarf Stellar Explosions

Novae: Recurrent Stellar Flares

The hydrogen build-up on the surface of a white dwarf can ignite into an explosive fusion reaction that blows off a shell of gas. Because so little mass is blown off during a nova, the explosion does not disrupt the binary system. Ignition of the infalling hydrogen can recur again with periods ranging from months to thousands of years.

White Dwarf Supernovae (Type Ia)

Subrahmanyan Chandrasekhar predicted that gravity will overcome the pressure of electron degeneracy if a white dwarf has a mass > 1.4 M_¤. Energetic electrons, which cause this pressure, reach the speed of light. If accretion brings the mass of a white dwarf above the Chandrasekhar limit, electron degeneracy can no... Continue reading "Stellar Endpoints: Supernovae, Neutron Stars, and Black Holes" »

Shock Waves: Formation and Mach Cone Angle

If the speed of a source relative to the medium exceeds the speed of sound in the medium, the Doppler equation no longer applies. In such a case, shock waves result. The half-angle of the Mach cone is given by:

Temperature Measurement and Thermometers

Temperature is an SI base quantity related to our sense of hot and cold. It is measured with a thermometer, which contains a working substance with a measurable property, such as length or pressure, that changes in a regular way as the substance becomes hotter or colder.

Zeroth Law of Thermodynamics: Thermal Equilibrium

When a thermometer and some other object are placed in contact with each other, they eventually reach thermal equilibrium. The reading of... Continue reading "Fundamental Concepts in Thermodynamics and Gas Behavior" »

Irreversible Processes and Entropy (S)

An irreversible process is one that cannot be reversed by means of small changes in the environment. The direction in which an irreversible process proceeds is set by the change in entropy ($S$) of the system undergoing the process. Entropy $S$ is a state property of the system.

Fundamentals of Electric Charge

The strength of a particle's electrical interaction with objects around it depends on its electric charge, which can be either positive or negative. Charges with the same sign repel each other, and charges with opposite signs attract each other.

An object with equal amounts of the two kinds of charge is electrically neutral, whereas one with an imbalance is electrically charged.

Conductors and Insulators

• Conductors

Write your text here!Bernoulli's theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar.