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

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" »

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" »

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.

Photons and Electrons in the Double Slit Experiment

Evidence for Wave-Particle Duality

• A single electron or photon leaves the source with particle-like discreteness and creates a single discrete spot on the screen.
• The interference pattern, which occurs over time, is a wave property.

Diffraction Pattern and Heisenberg’s Uncertainty Principle

• We cannot measure the exact position of each electron or its exact momentum as it approaches the slit; there is uncertainty in both position and momentum.
• The uncertainty in each electron’s y-position is reduced to the width of the slit (since we are certain it passes through the slit). This increases its uncertainty in the momentum of the y-direction.
• The uncertainty in the momentum in the y-direction means

Understanding Electrostatics

Electrostatics is the branch of physics that studies the phenomena produced by charges that do not vary or move.

History of Electrostatics

6th century BC: The Greeks discovered the electrical properties of amber. When rubbed, it could attract light objects.

18th century: Benjamin Franklin conducted experiments with different materials and observed that rubbed materials could either attract or repel each other.

Franklin's Theory of Electricity

• There are only two types of electricity: positive and negative.
• Electricity is a sort of fluid present in all objects and it can flow from one object to another by rubbing them.
• When there's an excess of electricity, objects have positive electricity, and when there's a lack of electricity,

Good morning today we are going to present the evolution of soccer balls.

Superball

The superball was a soccer ball that consisted of a chamber composed of a valve that prevented the air from coming out and a seam from outside to inside that was invisible and without a flange. This ball was the first ball made without tiento

Invention of the Invisible Tiento

In Bell Ville, in the Argentine province of Córdoba between 1929 and 1931 Romano Polo, Antonio Tossolini and Juan Valbonessi conducted numerous tests and trials that culminated in the invention of the ball with an invisible tiento, a ball that continued to be used for a couple of years.

Professional Use and Commemoration

The superball was first used professionally in the same year of its invention... Continue reading "Evolution of Soccer Balls: From Superball to Jabulani" »