Basic Physics Concepts

Overview

• Introduction to basic physics concepts: displacement, velocity, acceleration, projectile motion, Newton's laws, forces, momentum.

Distance vs Displacement

• Distance: How far something has traveled (scalar quantity, only magnitude).
• Displacement: Measures how far out of place an object is (vector quantity, includes direction).
  • Example: John walks 8 m east, then 3 m west.
    • Total distance = 8 + 3 = 11 m.
    • Displacement = 5 m (final position 5 m from the start).
• Key Point: Distance is always positive; displacement can be positive or negative.

Speed vs Velocity

• Speed: How fast an object is moving (scalar quantity, always positive).
  • Example: A car traveling at 30 m/s means it covers 30 m every second.
• Velocity: Speed with direction (vector quantity).
  • Example: 50 m/s west is a velocity.
  • Formulas:
    • Distance (D) = Velocity (V) x Time (T)
    • Average speed = Total distance / Total time
    • Average velocity = Displacement / Total time

Example Calculation

• Object moving at 50 m/s, traveling 1000 m:
  • Time = Distance / Speed = 1000 m / 50 m/s = 20 seconds.

Acceleration

• Acceleration: The rate of change of velocity (vector quantity).
  • Formula: Acceleration (a) = Change in Velocity (Δv) / Change in Time (Δt).
  • Example: Truck accelerating to 60 mph vs sports car.
  • Positive acceleration means increasing velocity; negative acceleration means decreasing velocity.

Table Example

• If initial speed is 12 m/s and acceleration is 4 m/s²:
  • Velocity at t=0: 12 m/s
  • Velocity at t=1: 16 m/s
  • Continues increasing by 4 m/s each second.

Projectile Motion

• Projectile: An object moving under the influence of gravity.
  • Analyze projectile motion in two dimensions (x and y).
  • Horizontal component (Vx) remains constant unless acted upon by a force.
  • Vertical component (Vy) changes due to gravitational acceleration (-9.8 m/s²).

Newton's Laws

• First Law: An object at rest stays at rest, and an object in motion stays in motion unless acted on by a net force.
• Second Law: F = ma (net force equals mass times acceleration).
  • Example Calculation: 10 kg mass with 80 N force results in 8 m/s² acceleration.
• Third Law: For every action, there is an equal and opposite reaction.

Key Takeaways

• Understand differences between scalar and vector quantities.
• Apply formulas for distance, speed, velocity, and acceleration.
• Analyze motion using Newton's laws and concepts of projectile motion.