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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

• Vx vs, t graphs

• Describing motion in words

• Data table

• Particle Model

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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

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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

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Making a Motion Diagram

3

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Examples of Motion Diagrams

5

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The Particle ModelA 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

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Position and TimeThe 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

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DisplacementThe change in the position of an object as it moves from initial position xi to final position xf is its displacement ∆x = xf – xi.

Slide 1-18

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Checking UnderstandingMaria 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

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AnswerMaria 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

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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

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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.