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

Light and Sound Waves

Light, when reflected from objects and reaching our eyes, allows us to see. Sound makes the eardrum—a membrane in the ear—vibrate. These vibrations are transmitted to the brain by nerves.

How Light Is Produced

The Sun is the main source of light on Earth. We have also learned how to produce light:

• Using chemical energy: Burning fuel produces light (e.g., wood, oil, and gas).
• Using electrical energy: This is the case with lamps, televisions, or computer screens.

How Sound Is Produced

• Intensity: Sounds can be strong or weak. Intensity is the magnitude that varies when we regulate the volume; it is measured in decibels.
• Tone: Sound can be high or low. Tone is the characteristic that differentiates two musical notes with the same

Conductors and Insulators

Materials that transmit heat well, such as metals like iron, are known as good conductors.

Materials that transmit heat poorly are known as bad heat conductors or insulators.

The Effects of Heat

Heat produces changes when it passes from one body to another. The primary effects include:

• Increases the temperature of bodies: This is the most noticeable change and the one we are most used to.
• Changes the state of bodies: For example, heat can melt ice and convert it into water.
• Expands bodies: This change is not generally noticeable to the naked eye.

Heat vs. Temperature: What's the Difference?

Many people confuse the concepts of heat and temperature. Although they are related, they are not the same.

Heat is a form of energy that... Continue reading "The Science of Heat: Conduction, Temperature, and Energy Transfer" »

English Grammar

Past Perfect

The past perfect tense describes actions that happened before another action in the past. It is formed using "had" + past participle.

Examples:

• I had worked for my uncle.
• I had met him before you introduced us.
• We had gotten married before 1985.

Third Conditional

The third conditional describes a hypothetical situation in the past that did not happen. It is formed using "if" + past perfect + "would have" + past participle.

Example:

If I had had enough money, I would have bought you a house. (Si hubiera tenido suficiente dinero, te hubiera comprado una casa)

Science

Celestial Bodies

Celestial bodies are objects in the universe that interact with each other through gravity. They can be classified into two types:

• Those that emit

The Doppler Effect

The Doppler Effect describes an increase or decrease in the frequency of sound, light, or other waves as the source and observer move toward or away from each other.

• When the sound source is approaching you, the frequency increases.
• When the sound source is moving away, the frequency decreases.

Application: Catching Speeding Motorists

The relative velocity between a police vehicle and a speeding car causes their distance to decrease. This effectively lowers the wavelength of the radar waves, resulting in a higher frequency, which is used to calculate the vehicle's speed.

Conductors and Superconductors

Conductors

A conductor is an object or material that allows the flow of an electrical current in one or more directions.

• Temperature

Essential Physics Definitions

Electricity and Circuits

• Grounding: Removing an excess charge by connecting an object to Earth.
• Lightning: The discharge of negative electrons at the bottom of thunderclouds to Earth's surface through ionized air.
• Electric Field: The area around an electric charge in which it shows its effect (attraction or repulsion).
• Positive Charge: Lines coming out from the charge.
• Negative Charge: Lines going into the charge.
• Electric Current: The flow of charged particles.
• Electric Power (Watts): The rate at which electric energy is transformed (e.g., a hair dryer).
• Power: The rate at which energy is transformed.
• Voltage: A source of potential difference that is less than the potential difference across the load (or battery terminals)

Ambient: simulate global lighting,  constant in all surfaces. Objects not lighted by extrnl source of light. Lghts parts that cannot be reached by source of light, but seen by  observer I = Ia*Ka

Diffuse: after a source of light incides in a surface, the reflected rays are dispersed in many directions (common: rough surfaces).A surface is an ideal diffuse reflector (Lambert reflector) if it reflects light in all directions with the = intensity → surface equally shiny from any perspective. I =Ip*Kp*(N*L)

Specular: effect of "bright spots" that see in a surface reflecting light, can only be observed from certain directions (common glossy surfaces) ▪ direction of specular reflection  determined by the angle of reflection (𝜙) with respect... Continue reading "3D Graphics Illumination and Surface Shading Techniques" »

newton’s laws of motion 1st when Net force acting on an object is zero, objects will not motion 2nd acceleration of an objects is equal to the net force acting On that object divided by the object mass 3rd when An object applies a force on the second object, the second object applies an Equal and opposite force to the first object in different object indifferent Direction.

Work: when a force is Apply on an object and it moves over a certain distance.

Friction: force that Resist motion of an object is called friction

The law of conservation of energy: it states that energy can neither be created nor Destroyed but can be transform one form to another

Distinguish between kinetic and potential energy: kinetic energy is the energy due to motion of... Continue reading "Coh3 chemical name" »

Static electricity:

• There are electrostatic forces between particles or objects with a positive or a negative charge.
• Charge is due to the surplus or defect of electrons.
• Like charges repel each other while opposite charges attract each other.
• Electric charge is measured in coulomb (C) and has the symbol Q.
• When there is an imbalance of positive and negative charge, we get a force between the charges according to Coulomb's law.

Electric current:

• Electric current is a flow of electrons or other charges through a material.
• Conductor: Electrons can move easily through the conductor.
• Insulator: It is very difficult for electrons to move through the material. The electrons are not free to move and form bonds.

Electrical Magnitudes:

• Potential difference is

Key Figures in Astronomical and Physical Science

Aristotle

• Proved that the Earth is spherical.
• Believed that the Earth was at the center of the universe.

Aristarchus

• He was the first to state that the Sun, and not the Earth, was the center of our universe.
• Used simple geometry to estimate the size of the Sun and Moon and their relative distances.

Ptolemy

• Made a model called the Ptolemaic system, concluding all astronomical objects move at constant speeds in circular orbits.
• Ptolemy built his model to fit this idea. The Ptolemaic model is one of the longest upheld scientific theories in history; it was the cornerstone of astronomy for 1,500 years.

Copernicus

• Concluded that the Sun was the center of the universe instead of the Earth.
• Promoted the concept

Arguments Against Earth's Rotation

1. Centrifugal Force and Stability

The Earth should have broken apart long ago due to centrifugal forces; since this does not happen, the Earth must be stationary.

2. The Problem of Falling Objects

If the Earth moved, falling objects would not strike the surface directly beneath their starting point because the surface would shift during the fall. Since objects fall in a straight line, the Earth cannot be moving.

3. Aerial Motion and Birds

If the Earth rotated, flying creatures like birds, which do not maintain constant contact with the surface, would be left behind. Since this is not observed, the Earth must be at rest.

4. Celestial Spheres and Natural Motion

Some argue that celestial bodies move independently within... Continue reading "Historical Arguments Against Earth's Rotation" »