Basic Concepts in Physics

Overview

• Topics covered: displacement, velocity, acceleration, projectile motion, Newton's laws, forces, momentum, etc.
• Ideal for beginners wanting to grasp fundamental physics principles.

Key Concepts

Distance vs. Displacement

• Distance: Total path traveled (scalar quantity).
  • Example: Distance from city A to city B = 100 miles.
• Displacement: Change in position, considering direction (vector quantity).
  • Example: John walks 8 m east and then 3 m west:
    • Distance traveled: 8m + 3m = 11m
    • Displacement: 5m east (final position - initial position).
• Scalar vs. Vector:
  • Distance = Scalar (magnitude only)
  • Displacement = Vector (magnitude + direction)

Speed vs. Velocity

• Speed: Rate at which distance is covered (scalar quantity).
  • Example: A car traveling at 30 m/s means it travels 30m every second.
• Velocity: Rate at which displacement occurs (vector quantity).
  • Velocity indicates both speed and direction.
• Formula:
  • Average Speed = Total Distance / Total Time
  • Average Velocity = Total Displacement / Total Time

Acceleration

• Acceleration: Rate of change of velocity (how fast velocity changes).
• Formula:
  • Acceleration = (final velocity - initial velocity) / time
• Positive acceleration = increased velocity; negative acceleration = decreased velocity.

Projectile Motion

• Any object influenced by gravity after release (ignoring air resistance).
• Projectile motion has:
  • Horizontal Component: Constant velocity (no acceleration in the x-direction).
  • Vertical Component: Decelerates due to gravitational acceleration (-9.8 m/s²).

Example of Projectile Motion:

• Ball kicked from a height:
  • Initial velocity components can be resolved:
    • (v_x = v \cos(\theta))
    • (v_y = v \sin(\theta))

Newton's Laws of Motion

1. First Law: An object remains at rest or in uniform motion unless acted upon by a net force.
   • Real-world illustration: A puck slides further on ice (less friction) versus on a rough surface (more friction).
2. Second Law: Net Force = Mass x Acceleration
   • Example calculation:
     • Force = 80 N, Mass = 10 kg
     • Acceleration = 80 N / 10 kg = 8 m/s²

Conclusion

• The lecture covers fundamental physics concepts, including definitions and formulas associated with displacement, velocity, acceleration, projectile motion, and Newton's laws, key for understanding basic principles in physics.