Introduction to Physics, Aerodynamics, and Light

Definition and Role of a Physicist

• Definition: A physicist is a scientist who studies the fundamental laws of nature, exploring how matter, energy, space, and time interact.

• Methodology:

  • They observe physical phenomena.

  • They develop mathematical models.

  • They conduct experiments to uncover why the universe behaves the way it does.

Notable International Physicists

• Albert Einstein ($1879$–$1955$)

  • Known as the "Father of Modern Physics."

  • Major Discoveries:

    • Theory of Relativity: Revolutionized the understanding of space, time, and energy.

    • Mass-Energy Equivalence: Represented by the famous equation $E = mc^2$.

    • Photoelectric Effect: Provided the explanation for this effect, which helped establish modern quantum physics.

  • Impact on Society:

    • The production of nuclear energy.

    • GPS technology relies on the principles of relativity for accuracy.

    • Influenced modern electronics and nuclear energy production.

• Isaac Newton ($1642$–$1727$)

  • An English physicist and mathematician.

  • Major Discoveries:

    • Laws of Motion: Formulated the fundamental laws governing the movement of objects.

    • Universal Law of Gravitation: Explained the force attracting objects with mass.

    • Studies on Light and Optics: Investigated the properties and behavior of light.

  • Inventions: Developed the reflecting telescope.

  • Impact on Society:

    • Forms the foundation of modern physics and engineering.

    • Applied in transportation, space exploration (satellites and ground stations), and construction.

• Galileo Galilei ($1564$–$1642$)

  • Known as the "Father of Modern Science."

  • Focused on the study of motion and falling objects.

  • Greatly improved the design and capability of the telescope.

• Marie Curie ($1867$–$1934$)

  • Major Discoveries:

    • Radioactivity.

    • Discovery of the elements Polonium and Radium.

  • Contributions to Science:

    • Pioneered research on radioactive elements.

    • First woman to win a Nobel Prize.

  • Impact on Society:

    • Development of treatments for cancer.

    • Advancement of medical imaging technologies.

• Michael Faraday ($1791$–$1867$)

  • Major Discoveries:

    • Electromagnetic Induction.

    • Principles of electric motors and generators.

  • Contributions to Science: Demonstrated the reciprocal relationship between electricity and magnetism (how electricity can generate magnetism and vice versa).

  • Impact on Society:

    • Provided the technical basis for electric generators, transformers, and power plants.

    • Enabled the widespread use of electricity.

• Nikola Tesla ($1856$–$1943$)

  • Major Discoveries:

    • Alternating Current ($AC$) system.

    • Tesla Coil.

  • Contributions to Science: Improved the efficiency of electrical transmission over long distances.

  • Impact on Society:

    • Modern electrical power distribution systems.

    • Power supply systems used globally.

Notable Filipino Physicists and Scientists

• Gregorio Y. Zara ($8 \, \text{March} \, 1902$–$15 \, \text{October} \, 1978$)

  • Filipino engineer and physicist.

  • Invention: Invented the first two-way video telephone.

  • Significance: Allowed callers and recipients to see each other while conversing, laying the groundwork for modern video-conferencing technology.

• Fe del Mundo

  • Major Contributions:

    • Pioneer in the field of Pediatrics.

    • Invented a low-cost incubator made of bamboo.

  • Impact on Society:

    • Improved healthcare for infants and children.

    • Specifically helped reduce infant mortality in rural areas.

• Dr. Casimiro del Rosario ($13 \, \text{June} \, 1896$–$15 \, \text{September} \, 1982$)

  • Named a National Scientist in the Philippines in $1983$.

  • Pioneer in the fields of physics, meteorology, and astronomy.

  • Research Areas:

    • Ultraviolet ($UV$) light of different wavelengths.

    • High voltage electrical discharges occurring in a vacuum.

Fundmentals of Fluids

• Definition of Fluids:

  • Any substance that flows and changes its shape to match the container it occupies.

  • Particles in a fluid can move freely past one another.

  • A substance that deforms and changes shape when subjected to force or stress.

  • Classification: Both liquids and gases are considered fluids.

• Properties of Fluids:

  • Density ($\rho$): The mass of fluid particles packed into a specific amount of space.

    • Standard Unit: $kg\,m^{-3}$.

  • Viscosity ($\mu$): A fluid's internal resistance to flow, described as its internal friction or stickiness.

    • Standard Unit: $Pa \cdot s$, $P$ (Poise), or $cP$ (centipoise).

• Pressure ($P$):

  • The amount of force applied to a specific area.

  • The physical force applied perpendicularly to a surface, divided by the area over which it is distributed ($P = \frac{F}{A}$).

  • It indicates the concentration of forces on an object.

  • Standard Units: Pa (Pascal), atm (atmosphere), mmHg (millimeters of mercury), torr, and bar.

• Air Pressure (Atmospheric Pressure):

  • The force exerted by the weight of the Earth's atmosphere pushing down on a surface.

  • Altitudinal Changes:

    • Pressure decreases with higher altitude.

    • At higher altitudes, air is less dense; fewer molecules in a volume result in lower pressure.

    • Gravity is weaker further from the Earth's center, allowing molecules to spread out or become "thinner."

  • Other factors affecting air pressure include temperature and weather patterns.

• Pressure-Volume Relationship:

  • Squeezing a balloon results in an increase in pressure as the volume decreases.

  • This relationship is known as Boyle's Law.

Aerodynamics and Fluid Motion

• Definition:

  • A branch of fluid mechanics studying the motion of air and other gases.

  • Studies the forces created when objects move through gases.

  • The study of how air flows in and around objects of all sizes.

• Relative Wind:

  • The breeze felt when moving through air (e.g., riding a bicycle or putting a hand out of a moving car).

  • It always blows parallel and directly opposite to the direction of travel.

• The Continuity Principle:

  • When a flowing fluid is forced into a narrower path, it must speed up to pass through.

  • Equation: $A_1 v_1 = A_2 v_2$

  • Increasing the area decreases the speed.

  • Decreasing the area increases the speed.

• Bernoulli's Principle:

  • Formulated by Daniel Bernoulli.

  • States that as the speed of a fluid increases, the pressure within the fluid decreases.

  • Follows the Law of Conservation of Mechanical Energy.

  • Conservation of Mechanical Energy Equation: $mgh_i + \frac{1}{2} mv_i^2 = mgh_f + \frac{1}{2} mv_f^2$

  • Bernoulli's Principle Equation: $P_i + \rho g h_i + \frac{1}{2} \rho v_i^2 = P_f + \rho g h_f + \frac{1}{2} \rho v_f^2$

  • Simplified form: $P + \frac{1}{2} \rho v^2 = \text{Constant}$

Key Forces in Aerodynamics

• Lift: The upward aerodynamic force generated by wings (or airfoils) as the aircraft moves through air.

• Weight (Gravity): The downward force pulling the aircraft toward the center of the Earth.

• Thrust: The forward force produced by the propulsion system; it overcomes air resistance to drive the aircraft forward.

• Drag: The rearward, retarding force caused by disruption of airflow around the aircraft structure; acts parallel to the relative wind and opposes forward motion.

Airspeed Concepts and Types

• Definition: Airspeed is the speed of an aircraft relative to the surrounding air mass. It is used to calculate lift, drag, and structural limits via dynamic pressure.

• Types of Airspeed ($ICE-T$):

  1. Indicated Airspeed ($IAS$):

     • Direct reading from the airspeed indicator ($ASI$).

     • Measures raw dynamic pressure entering the pitot tube.

     • Uncorrected for atmospheric density, installation, or instrument errors.

     • Used for performance limits (takeoff, landing, stall speeds) because wings react to actual air density/pressure regardless of altitude.

  2. Calibrated Airspeed ($CAS$):

     • $IAS$ corrected for installation and instrument errors.

     • Fixes mechanical discrepancies caused by air flowing around the aircraft, especially at high angles of attack or low speeds.

  3. Equivalent Airspeed ($EAS$):

     • $CAS$ corrected for the compressibility of air.

     • At high speeds, air compresses in front of the pitot tube, creating an artificially high reading.

     • Used for structural engineering and high-performance aircraft calculations.

  4. True Airspeed ($TAS$):

     • The actual speed relative to the air mass.

     • $EAS$ (or $CAS$ at low speeds) corrected for non-standard altitude and temperature.

     • Aircraft must fly faster at higher altitudes (lower density) to cause the same pressure difference at the pitot tube as at sea level.

Properties and Behaviors of Light

• Definition: Fundamental form of energy known as electromagnetic radiation.

  • Consists of oscillating electric and magnetic fields.

  • Does not require a medium; can travel through a vacuum.

• Core Behaviors:

  1. Reflection: Bouncing of light off surfaces.

  2. Refraction: Bending of light as it enters a new material.

  3. Dispersion: Separation of light into component colors (e.g., via a prism).

  4. Diffraction: Spreading of light around edges or through small openings.

  5. Interference: Combination of light waves to form patterns of brightness and darkness.

  6. Polarization: Restriction of light vibrations to a particular direction.

• Color and the Visible Spectrum:

  • Color is determined by the frequency (or wavelength) of light.

  • Visible Spectrum: Ranges from red (lowest frequency, longest wavelength) to violet (highest frequency, shortest wavelength).

  • White Light: A combination of all visible colors.

• Human Vision:

  • The retina contains specialized cells:

    • Rods: Sensitive to brightness (responsible for black and white vision).

    • Cones: Three types sensitive to red, green, or blue light.

• Absorption and Reflection:

  • Selective Reflection: Objects appear colored because they reflect specific wavelengths and absorb others.

    • A red rose reflects red light; if illuminated by light without red, it appears black.

    • White objects reflect all colors equally; black objects absorb all colors.

  • Selective Transmission: Transparent materials (like colored glass) appear as the color they transmit; energy from absorbed light warms the glass.

Color Mixing and Wave Interference

• Additive Mixing (Light):

  • $Red + Green = Yellow$

  • $Red + Blue = Magenta$

  • $Blue + Green = Cyan$

  • $Red + Green + Blue = White$

• Subtractive Mixing (Paint/Pigment): Mixing pigments results in more light being absorbed, creating darker colors.

• Complementary Colors: Two colors that combine to produce white light.

• Wave Interference:

  • Constructive Interference: Waves add together to create brighter regions.

  • Destructive Interference: Waves cancel each other to create darker regions.

  • Interference patterns are formed when two or more light waves overlap.