Ch. 2 Representing Motion

2.1 Picturing Motion Motion Diagrams A series of images of a moving object that records its position after each equal time interval Figures 2-3

The Particle Model Use a point to represent the body in motion. Disregard the arms and legs or the wheels The point is placed at the center of gravity. The process is called the particle model. Creates a simplified version of the object

2.2 Where and When?

Coordinate Systems Sets up the beginning of the event Defines the zero point (origin) or the starting point Defines the direction of increasing values Some events require 2 dimensions x-axis (horizontal) and y-axis (vertical)

Locate the object at any time in the event based on the defined coordinate system Position vector is an arrow that indicates where the object is at a given time from the origin

Vectors and Scalars Scalar quantity- indicated only the magnitude of something Tells how big or small Vector quantity- indicated magnitude and also direction of the object. This book makes the symbol bold faced to represent a vector Resultant is the sum of the other vectors

Time Intervals and Displacements Displacement-defines the distance and the direction between two positions Vector quantity Distance-only indicates how far from the origin Scalar quantity Time interval-the time for an event

Time on the x-axis and position (displacement) on the y-axis 2.3 Position-Time Graphs Time on the x-axis and position (displacement) on the y-axis

Equivalent Representations Many different ways to describe motion. Depends upon what you want to find out as to what method you would use. Words, pictures, motion diagrams, data tables, position-time graphs