Introduction to Physics

What is Physics?

• Physics is derived from the Greek word "fusis," meaning nature or natural things.
• Physics deals with the conceptual understanding involving theories, laws, and principles that explain different phenomena.
• Physics uses mathematics as a tool when solving for physical quantities.
• Physics is a branch of natural science dealing with matter, energy, and their interactions.

Branches of Physics

• Classical Physics:
  • Mechanics studies the motion of macroscopic bodies and how matter and forces interact.
    • Kinematics describes motion without considering forces, using mathematics.
    • Dynamics is about the behavior of objects under external forces, linking kinematics to the cause of motion (force).
  • Thermodynamics studies heat transfer, its changes, and its relationship with other forms of energy.
  • Electromagnetism deals with the relationship between electricity and magnetism.
  • Optics studies the physical properties of light, its nature, behavior, light, vision, and electromagnetic radiation phenomena.
• Modern Physics:
  • Atomic Physics studies matter at the atomic scale.
  • Biophysics applies physics to study living organisms.
  • Chemical Physics uses physics principles to study chemical processes.
  • Cryogenics studies material behavior at very low temperatures.
  • Fluids Physics studies behavior of gases and liquids.
  • Geophysics studies the earth using physics principles.
  • Health Physics involves radiation for people working nearby.
  • Mathematical Physics emphasizes mathematics as a medium for understanding physics; new laws can be expressed mathematically.
  • Nuclear Physics studies the structure and properties of the atomic nucleus and applications.
  • Plasma Physics deals with the behavior and properties of fully ionized plasma.
  • Planetary Physics studies the planets.
  • Quantum Physics studies the quantum theory, matter interactions, and electromagnetic radiation.
  • Relativity describes objects moving at nearly the speed of light.
  • Solid-state physics examines the structures and properties of materials using quantum mechanics.
  • Space Physics is the study of planetary and interplanetary magnetized plasmas.

Measurement

• Measurement compares an unknown quantity to a standard.
• Fundamental Quantity is measured directly: length, mass, time, temperature, luminous intensity, electric current, amount of substance.
• Derived Quantity combines fundamental quantities: area, volume, density, velocity, acceleration, force, work, power, energy.
• A system of measurement sets standards for specific quantities.
• The metric system's measurement standards are precise.
  • MKS = meter-kilogram-second.
  • cgs = centimeter-gram-second.

Motion

• Distance is a scalar quantity: how far an object has traveled.
• Displacement is a vector quantity: object's position from its starting point.
• Speed is a scalar quantity: how fast an object is moving.
• Velocity is a vector quantity: the rate at which an object changes position.
• Types of Motion:
  • Uniform Motion is constant velocity or speed in a straight line.
  • Uniformly Accelerated Motion's velocity changes constantly.
    • Acceleration is defined as the rate of change of velocity per unit time.

Free Fall

• Freefall considers gravity as the only acting force.
• Free-fall motion is uniformly accelerated motion due to gravity, which is 9.8m/s².
• Velocity, displacement, and acceleration are positive when directed upwards and negative when downwards.

Projectile Motion

• Two-Dimensional Motion is an object that can have a path that lies in a plane.
• Projectiles are objects thrown into the air.
• A projectile moves in horizontal and vertical paths simultaneously.
• Trajectory is the path of a projectile which often makes that shape of an inverted parabola
  • Horizontally, the projectile moves uniformly.
  • Vertically, the projectiles accelerate where acceleration is due to gravity.

Newton's Laws of Motion

• Isaac Newton explains why objects move using his laws of motion.
• Law of Inertia:
  • Objects at rest stay at rest, and objects in motion stay in motion unless acted upon by an unbalanced force.
  • Objects resist changes in motion, which is called inertia.
  • Inertia is measured by mass.
  • At rest, forces are balanced, making velocity zero.
  • Force is a push or a pull.
  • Contact force is applied directly.
  • Non-contact forces are gravitational, electric, and magnetic forces.
  • An object in equilibrium is when all forces are balanced.
• Law of Acceleration:
  • The behavior of objects under unbalanced forces.
  • Unbalanced forces or net force causes acceleration.
  • Acceleration is directly proportional to the net force and inversely proportional to mass.
  • The net force easily accelerates an object.
  • Net force is the vector sum of all forces.
  • More massive objects are harder to accelerate.
  • With greater net force, it is easier to slow down an object in motion.
• Newton's Third Law of Motion:
  • Contact forces include normal, frictional, tensional, and applied forces.
  • When objects interact, each exerts forces on the other.
  • Law of Interaction: For every action, there is an equal and opposite reaction.
  • For every force, there is a reaction force, that is equal in magnitude, but opposite in direction.