Physics Notes on Distance and Displacement

Distance and Displacement

• Overview of Linear Motion
  • Year 10 Physics Topic focusing on rectilinear motion (straight-line motion).

Centre of Mass

• Concept of Centre of Mass
  • Used to simplify complex motions.
  • Example: A freestyle swimmer moving at a constant speed of 2 m/s.
  • Head and torso move at 2 m/s forward.
  • Arms have more complex motion (sometimes faster or slower).
  • Centre of mass is the balance point of an object, representing overall motion.

Position

• Definition of Position
  • Describes the location of an object at specific time relative to an origin.
  • Vector Quantity: Requires direction for full understanding.
• Example with the swimmer:
  • At point a: Position = -10 m (10 m behind the origin)
  • At point b: Position = 0 m (on the starting block)
  • At point c: Position = +25 m (25 m to the right of origin)

Distance Travelled

• Definition
  • Total path length covered during a journey, irrespective of direction.
• Example with a car:
  • Odometer reading increases with distance travelled regardless of direction.

Displacement

• Definition
  • Change in position of an object, considering only the start and endpoint.
  • Route taken does not affect displacement.
  • Sign of Displacement: Indicates the direction of position change.
• Example:
  • A lift travels:
  • From ground floor to basement: Displacement = -10 m (10 m downward)
  • From basement to top floor: Displacement = +60 m (60 m upward)
  • Total trip:
  • Distance travelled = 70 m
  • Overall displacement = +50 m (50 m upward)