Lecture on Motion in Physics

Introduction

• Rest and Motion: Objects at rest vs. in motion
  • Rest: No change in position
  • Motion: Change in position

Types of Motion

• Regular and Controlled: e.g., watch
• Erratic and Uncontrolled: e.g., tsunami

Study of Motion in Physics

• Helps in controlling motion for constructive purposes (e.g., hydroelectric dam)
• Key Learning Objectives:
  • Define motion
  • Identify instances of motion in everyday life
  • Analyze motion along a straight line
  • Identify uniform and non-uniform motion
  • Calculate speed and average speed
  • Define and calculate velocity
  • Explain scalar and vector quantities
  • Define and calculate acceleration

Everyday Examples of Motion

• Birds flying, horses galloping, water flowing, cars moving
• Definition of Motion: Change in position with respect to surroundings and time

Relativity of Rest and Motion

• Car Driver Example:
  • Rest with respect to the car
  • Motion with respect to surroundings
• Bus Example:
  • Trees and objects outside appear moving to passengers
  • Passengers appear at rest to one another

Dimensions of Motion

• One-Dimensional (Linear): Motion along a straight line
  • Example: Cars moving on a straight path
• Two-Dimensional: Motion in two directions in a plane
  • Example: Golf ball trajectory
• Three-Dimensional: Motion in three directions
  • Example: Airplane taking off
• Focus on linear motion in this lesson

Distance and Displacement

• Distance: Actual length of the path covered
  • Example: Mary’s travel from home to school to playground
• Displacement: Shortest distance between initial and final points
  • Example: Straight line from Mary’s home to playground

Uniform and Non-Uniform Motion

• Uniform Motion: Equal distances in equal intervals of time
  • Example: Yellow car in the race
• Non-Uniform Motion: Unequal distances in equal intervals or equal distances in unequal intervals
  • Example: Red car in the race

Speed

• Definition: Rate at which an object covers distance
• Formula: Speed = Distance / Time
• Units: cm/s (CGS), m/s (SI), km/h
• Example Calculation: Mary’s speed walking to school
• Average Speed: Total distance / Total time

Velocity

• Definition: Speed in a definite direction
• Formula: Velocity = Displacement / Time
• Units: cm/s, m/s, km/h
• Average Velocity: Total displacement / Total time

Scalar and Vector Quantities

• Scalar: Only magnitude (e.g., distance, speed)
• Vector: Magnitude and direction (e.g., displacement, velocity)

Acceleration

• Definition: Rate of change of velocity
• Formula: Acceleration = (Final Velocity - Initial Velocity) / Time
• Units: cm/s² (CGS), m/s² (SI)
• Uniform Acceleration: Equal change in velocity per unit time
  • Example: Freely falling object
• Non-Uniform Acceleration: Unequal change in velocity
  • Example: Car negotiating a turn
• Negative Acceleration (Retardation): Decrease in velocity
  • Example: Bus coming to a halt

Summary of Quantities

• Distance: Length of motion
• Displacement: Distance with direction
• Speed: Change in distance over time
• Velocity: Change in displacement over time
• Acceleration: Change in velocity over time

Graphical Representation of Motion

• Importance of Graphs: Visual representation, easier understanding
• Distance-Time Graphs: Show change in position over time
  • Types: Object at rest, uniform motion, non-uniform motion
• Velocity-Time Graphs: Show change in velocity over time
  • Types: Object at rest, uniform velocity, uniform acceleration, non-uniform acceleration, uniform retardation
  • Use: Determine displacement, acceleration, velocity

Equations of Motion

• First Equation: v = u + at
• Second Equation: s = ut + ½at²
• Third Equation: 2as = v² - u²
• Used to determine position, velocity, and acceleration

Uniform Circular Motion

• Example: Athlete running on circular track
• Formula: v = 2πr / t (where r is radius and t is time)
• Examples: Moon’s rotation, satellite orbits

Conclusion

• Review: Key points and concepts from the lesson
• Practical Applications: Solved problems and flashcards for revision