Lecture on Distance, Displacement, and Speed

Objectives

• Understand the difference between distance and displacement.
• Define speed.
• Calculate the speed of a moving object.

Key Concepts

Distance

• Definition: How far an object moves.
• Characteristics:
  • Does not involve direction.
  • Scalar quantity (has magnitude but no direction).
• Example: A car moves 500 meters along a road.

Displacement

• Definition: Distance moved in a straight line from the start to the endpoint.
• Characteristics:
  • Includes the direction of the straight line.
  • Vector quantity (has both magnitude and direction).
• Example: Displacement of 380 meters east.

Speed

• Definition: Distance an object travels in a given time.
• Formula:
  • Speed (v) = Distance (s) / Time (t)
• Characteristics:
  • Scalar quantity (does not involve direction).
  • Not given in exams, must be memorized.

Calculation Example

Problem

• A car travels 260 meters in 20 seconds.
• Calculation:
  • Speed = 260 meters / 20 seconds = 13 meters per second.

Typical Speeds

• Walking Speed: ~1.5 meters per second.
• Running Speed: ~3 meters per second.
• Cycling Speed: ~6 meters per second.
• Car on Main Road: ~13 meters per second.
• Fast Train in UK: ~50 meters per second.
• Cruising Airplane: ~250 meters per second.
• Speed of Sound in Air: ~330 meters per second (varies with temperature).

Factors Affecting Speed

• Individual fitness: Younger, fitter people often faster.
• Terrain: Flat ground allows faster movement than uphill.
• Distance traveled: Faster at the start of long distances.

Average Speed and Constant Speed Calculations

• Speed is rarely constant; average speed is used for ease.
• Distance Calculation:
  • Rearranged formula: Distance = Speed x Time

Calculation Example

• Problem: A car travels at 12 meters per second for 8 seconds.
• Solution:
  • Distance = 12 m/s × 8 s = 96 meters.

Additional Resources

• Practice questions available in the revision workbook.
• Link to further materials provided in the video.