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

Understanding Waves and Energy Transfer

A wave is a disturbance that travels a distance, carrying the energy which generated it. When the wave travels through a medium, like water or air, it does not displace the particles of the medium.

Characteristics of a Wave

• Wavelength: This is defined as the distance between two adjacent peaks or troughs of the wave. It is expressed in metres (m).
• Frequency: This is the number of oscillations or complete movements that a wave produces in one second. Its unit in SI is the Hertz (Hz).
• Speed of Propagation: This is the distance, e, that the wave travels divided by the time taken, t. It is expressed in m/s.

  Waves travel at a constant speed. Therefore:

  V_wave = e/t

  Which implies:

  e = V_wave · t

• Amplitude: This is the

Essential Wave Phenomena Definitions

Wave Terminology

• Node: A point of zero amplitude on a standing wave.
• Resonance: The increase in the amplitude of a vibration that occurs when external vibrations match an object's natural frequency.
• Antinode: A point of maximum amplitude on a standing wave.
• Standing Wave: A wave that appears to stand in one place, even though it is really two waves interfering as they pass through each other.
• Reflection: The bouncing back of an object or a wave when it hits a surface through which it cannot pass.
• Hertz (Hz): Unit of measurement for frequency.
• Frequency: The number of complete waves that pass a given point in a certain amount of time.
• Wavelength: The distance between two corresponding parts of a wave.
• Amplitude: The

Human Evolution: From *Orrorin* to *Homo Sapiens*

The Earth was formed 4,500 million years ago. There is evidence that the hominid family emerged 6 million years ago, with our species, Homo sapiens sapiens, appearing only 150,000 years ago. Our species is characterized by the development of the brain, which allows for complex social behavior, consciousness of our own existence, and a great capacity for communication. The evolution of our species includes the following:

Key Hominid Species

1. Orrorin tugenensis: Lived more than 6 million years ago (MA). They were omnivorous, lived in jungles, measured 1.4 meters, were bipedal, and were descendants of the current chimpanzees, but with differences in the pelvis, humerus, and femur.
2. Ardipithecus ramidus:

INDUCTION / magnetic flux density: the number of lines of force crossing the unit area.

Paramagnetic material: when placed in a magnetic field and become magnets are oriented in the same direction as the field. Magnetic field to cease its magnetism disappears. (weakly attracted) Cr, Al ..

Diamagnetic material: when placed inside a magnetic field, are magnetized in the opposite direction to the field. These substances are called diamagnetic and their property is called diamagnetism. (weakly repelled) Na, Cu, N, H. .. .

Ferromagnetic materials: the electron spins tend to align because of the forces between them and form small regions called domains. By placing these substances under the action of a field, partially oriented domains and grow... Continue reading "Understanding Magnetic Materials: Flux, Saturation, and Permeability" »

Michelangelo's David is a monumental sculpture depicting the biblical King David. Rendered in a classical style, he is completely nude and portrayed as an athlete, carrying a sling in his left hand (resting on his shoulder) and a stone in his right. Facial features are clearly visible, along with curly hair, defined musculature, and a pronounced contrapposto.

Symbolic Analysis of David

Michelangelo depicted King David not merely as a young athlete, but as a man in the prime of his life. The artist chose as the subject of the work the moment prior to the confrontation between David and Goliath, unlike other representations where Goliath's defeated head often appears at his feet. Therefore, the figure displays a contained and expectant gaze, imbuing... Continue reading "Michelangelo's David: Form, Symbolism, and Florentine Identity" »

Aristotle's Cosmic Conception

Aristotle, in the fourth century BC, distinguished two regions of the universe:

The Terrestrial Region (Below)

• Earth occupies the center of the universe.
• All terrestrial bodies are formed by combining four elements: earth, water, air, and fire.
• Earth is the heaviest element and tends downwards, while fire tends upwards.

The Celestial Region (Above)

• It consists of transparent, concentric spheres surrounding the Earth.
• In each sphere, one of the heavenly bodies (Sun, Moon, Venus, etc.) is located.
• The outermost sphere contains the fixed stars.

Ptolemy's Geocentric System

Developed by Ptolemy (2nd Century AD), this system placed Earth at the center of the universe and described the movements of celestial bodies using Earth as... Continue reading "Evolution of Astronomical Models: From Ancient Cosmos to Newton" »

Energy: The Driver of Change

Energy drives all changes and movements in the universe and our daily lives. The main forms of energy include:

• Heat: Energy from sources like the sun, ovens, and dryers.
• Electricity: The most essential and widespread power in modern societies, used for lamps, phones, and computers.
• Chemical: Produces movement, heat, and electricity, such as burning gasoline in engines or chemical reactions in batteries.
• Kinetic: Energy possessed by bodies in motion; the higher the speed, the greater the kinetic energy.
• Potential: Energy stored in bodies based on their height above the ground; the greater the height, the more potential energy.

Understanding Movement

• Path of Movement: The different positions occupied over time.
• Position: The

Early Greek Conceptions: The Ionian School

Some Greek thinkers made the first attempts to conceive the world as the result of natural processes, rather than an incomprehensible work of the gods. This was notably the case for the philosophers of the Ionian school, which flourished around the 6th century BC.

According to their views, the universe was initially in a state of primordial unity, where everything was mixed. From this unity, pairs of opposites arose, interacting with each other. These interactions led to the formation of heavenly bodies on one hand, and the Earth with its plants and animals on the other.

The Ionian philosophers conceived the Earth as a flat disk floating in the center of the celestial sphere.

The Spherical Earth: Pythagoras

Deriving Key Physics Formulas

Deriving v = u + at

    → v = u + at

Deriving s = ut + ½ at²

V_average =     But v = u + at       → V_average =  

V_average = s/t    → s = V_average(t)    → s = (t)     → s = ut + ½ at²

Deriving v² = u² + 2as

v = u + at   → v² = u² + 2uat + (at)²    {multiply out both sides}

We can rewrite this as v² = u² + 2a(ut + ½ at²)             {because 2a(ut + ½ at²) = 2uat + (at)²}

Now sub in s = ut + ½ at²    → v² = u² + 2as

Force and Motion

- F = Bqv: Consider a section of conductor of length l through which a current I is flowing.

If q is the charge which carries the current in this section of the conductor, then:

I = q/t, where t is the time it takes the charge q to travel

Direction of Electric Current

If you consider the position of a compass needle around a conductor carrying an electric current, you can establish a relationship between the direction of the current and the resulting magnetic field.

Please note the following: Electricity flows due to the movement of electrons through the conductor. Even before the existence of electrons was discovered, the flow direction of the stream was established. It was agreed that the current runs from the positive terminal of a power source to the negative terminal. (The conventional sense of the current is opposite to the actual motion of electrons; we use the conventional sense of the current in analysis.)

Indication of Current Direction in Diagrams

To characterize the... Continue reading "Electric Current Direction: Conventional Flow and Electron Motion" »