© 2010 Pearson Education, Inc. General Motion and Constant Velocity Motion General Motion Model - Definitions Position Distance Displacement Average Speed Average Velocity Instantaneous Speed Instantaneous Velocity Constant v motion - Representations of motion Motion Diagram X vs. t graphs V x vs, t graphs Describing motion in words Data table Particle Model

© 2010 Pearson Education, Inc. Using Mastering Physics Start Early Write solutions on paper (Work offline if possible) Don’t use more than 2-3 submissions for tweaking even when you are sure you are correct Before each submission, check your work carefully Check your units and significant figures When you need help Present your reasoning and calculations as well as your answers Make sure you are using key concepts and definitions from class or the textbook

© 2010 Pearson Education, Inc. How to describe motion What information do you need to communicate to be able to tell someone how to reproduce a motion? Frame of reference or reference frame Origin Where to start What direction to start moving What speed to start moving with Changes in direction or speed How far to go? (Where to stop) Timing

© 2010 Pearson Education, Inc. Making a Motion Diagram 3

© 2010 Pearson Education, Inc. Examples of Motion Diagrams 5

© 2010 Pearson Education, Inc. The Particle Model A simplifying model in which we treat the object as if all its mass were concentrated at a single point. This model helps us concentrate on the overall motion of the object. Slide 1-16

© 2010 Pearson Education, Inc. Position and Time The position of an object is located along a coordinate system. At each time t, the object is at some particular position. We are free to choose the origin of time (i.e., when t = 0). Slide 1-17

© 2010 Pearson Education, Inc. Displacement The change in the position of an object as it moves from initial position x i to final position x f is its displacement ∆x = x f – x i. Slide 1-18

© 2010 Pearson Education, Inc. Checking Understanding Maria is at position x = 23 m. She then undergoes a displacement ∆x = –50 m. What is her final position? A.–27 m B.–50 m C.23 m D.73 m Slide 1-19

© 2010 Pearson Education, Inc. Answer Maria is at position x = 23 m. She then undergoes a displacement ∆x = –50 m. What is her final position? A.–27 m B.–50 m C.23 m D.73 m Slide 1-20

© 2010 Pearson Education, Inc. Trials 1-3 Summary Slide 1-7 Constant velocity motion Straight line position vs. time graph Slope shows how fast you are moving Steeper Slope => faster speed Velocity vs. Time Graph is flat straight line Faster => farther from time axis Spacing of Balloons is the same Faster speed => distance between balloons increases

© 2010 Pearson Education, Inc. Trials 4-6 Slide 1-7 Trial #4: Walk in a straight line toward the motion detector at a constant, regular walking pace. Trial #5: Walk in a straight line toward the motion detector at a constant, fast pace. Trial #6: Walk in a straight line toward the motion detector at a constant, slow pace.