Basic Physics Concepts

Jul 22, 2024

Basic Physics Concepts

Topics Covered

  • Displacement
  • Velocity
  • Acceleration
  • Projectile Motion
  • Newton's Three Laws
  • Forces
  • Momentum

Distance and Displacement

  • Distance: How far something has travelled. Scalar quantity (magnitude only).
    • Example: Distance between two cities could be 100 miles.
  • Displacement: Distance + Direction. Vector quantity (magnitude and direction).
    • Example: John walks 8 meters east, then 3 meters west.
      • Total distance = 11 meters
      • Displacement = 5 meters (8 - 3)
  • Scalar Quantity: Only magnitude.
  • Vector Quantity: Magnitude and direction.
  • Displacement can be positive or negative based on direction.

Speed vs. Velocity

  • Speed: How fast something is moving. Scalar quantity (positive).
    • Example: 30 meters per second means every second an object travels 30 meters.
    • Formula: d = vt
  • Velocity: Speed with direction. Vector quantity (can be positive or negative).
    • Example: 30 meters per second going west.
    • Average Speed: total distance / total time
    • Average Velocity: displacement / total time
  • Formulas:
    • Average Speed: v̄ = d / t
    • Average Velocity: v̄ = Δx / t

Acceleration

  • Acceleration: How fast velocity is changing. Vector quantity.
    • Formula: a = Δv / Δt
    • Example: Sports car vs. truck accelerating from 0 to 60 mph.
  • Acceleration due to Gravity (g): Vertical acceleration affecting velocity.
    • On Earth: g = -9.8 m/s²
    • Affects vertical component of velocity, not horizontal.
    • Formulas:
      • v_f = v_i + at
      • Gravitational Acceleration: Examples:
        • Object released from rest: Vertical velocity continuously decreases.
        • Object thrown upwards: Vertical velocity decreases by 9.8 m/s every second.

Projectile Motion

  • Projectile: Object moving under gravity's influence.
    • One-Dimensional Motion: Vertical direction (y-direction).
      • Examples: Ball falling or thrown straight up.
    • Two-Dimensional Motion: Horizontal (x-direction) and vertical (y-direction).
      • Example: Ball rolling off a cliff or kicked at an angle.
    • Horizontal velocity (v_x) remains constant, vertical velocity (v_y) changes due to gravity.
    • Formulas:
      • v_y = v sin(θ)
      • v_x = v cos(θ)

Newton’s Three Laws of Motion

  • First Law: Object at rest stays at rest, object in motion stays in motion unless acted on by an external force.
    • Example: Box remains still unless a push or pull force is applied.
  • Second Law: F = ma
    • Example: 10 kg box with 80 N force → acceleration = 8 m/s²
      • Velocity increases by 8 m/s every second if the force is continuously applied.
  • Third Law (Implied but not detailed in transcript): Every action has an equal and opposite reaction.