Basic Physics Concepts Lecture Notes

Overview

• Topics Covered: Displacement, Velocity, Acceleration, Projectile Motion, Newton's Three Laws, Forces, Momentum.
• Purpose: Introduction to basic physics principles.

Distance and Displacement

• Distance: Scalar quantity, only has magnitude. Example: Distance between two cities (100 miles).
• Displacement: Vector quantity, has both magnitude and direction. Example: Walking 8 meters east then 3 meters west results in a displacement of 5 meters east (8 - 3).
• Key Difference: Distance is always positive, displacement can be positive or negative depending on direction.
• Example: Traveling 200 miles vs. Traveling 300 miles north (distance vs. displacement).

Speed and Velocity

• Speed: Scalar quantity, measures how fast something is moving. Example: Car traveling at 30 meters per second.
• Velocity: Vector quantity, measures speed with direction. Example: Train moving at 30 meters per second west.
• Key Difference: Speed is always positive, velocity can be positive or negative.
• Formulas:
  • Average Speed = Total Distance / Total Time
  • Average Velocity = Displacement / Total Time
• Example: Object traveling 12 meters east and then 20 meters west in 4 seconds.
  • Average Speed = 32 meters / 4 seconds = 8 m/s
  • Average Velocity = -8 meters / 4 seconds = -2 m/s

Acceleration

• Definition: Change in velocity over time. Example: Sports car accelerating faster than a truck.
• Formula: Acceleration (a) = Change in Velocity (Δv) / Time (t)
• Example: Truck vs. Sports Car from 0 to 60 miles per hour.
• Positive vs. Negative Acceleration: Positive acceleration increases velocity, negative acceleration decreases velocity.
• Formulas:
  • Final Velocity = Initial Velocity + (Acceleration * Time)
• Example: Object with initial velocity of 12 m/s east and acceleration of 4 m/s².
  • Velocity after 1 second = 16 m/s
  • Velocity after 2 seconds = 20 m/s

Gravitational Acceleration

• Earth's Gravitational Acceleration (g): -9.8 m/s².
• Example: Ball dropped from rest vs. thrown upward.
• Effect on Velocity: Decreases by 9.8 m/s every second (for Earth).
• Components: Horizontal (v_x) and Vertical (v_y) components of velocity.

Projectile Motion

• Definition: Object moving under the influence of gravity, typically ignoring friction.
• Horizontal and Vertical Components: Horizontal velocity (v_x) remains constant, vertical velocity (v_y) changes due to gravity.
• Example: Ball kicked off a cliff vs. kicked at an angle.
• Formulas:
  • v_x = v * cos(θ)
  • v_y = v * sin(θ)

Newton's Three Laws of Motion

Newton's First Law

• Inertia: Object at rest stays at rest, object in motion stays in motion unless acted upon by a net force.
• Examples: Box at rest, box sliding with and without friction.

Newton's Second Law

• Formula: Net Force (F) = Mass (m) * Acceleration (a).
• Example: 10 kg mass with 80 N force.
  • Acceleration = 80 N / 10 kg = 8 m/s²
  • Velocity changes over time due to applied force.