© 2010 pearson education, inc. week 3 day 2: topics slide 1-7 particle model general motion model...

© 2010 Pearson Education, Inc.

Week 3 Day 2: Topics

Slide 1-7

Particle Model

General Motion Model

Constant Velocity Model

Representations of Motion

• Motion Graphs

• Motion Diagrams

•Velocity graph to Position


Announcements:

Slide 1-7

Particle Model




• Motion Graphs

• Motion Diagrams



Homework Hints:

Slide 1-7

Particle Model




• Motion Graphs

• Motion Diagrams



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

© 2010 Pearson Education, Inc. Slide 1-7

Can you move?

Fill in the tables for these motion events by indicating whether or not a motion event is possible. If it is, give an example. If not, explain why not.Displacement Final Position Possible? Example/Explanation

0 00 Not 0

Not 0 0Not 0 Not 0

Average Speed Average Velocity

Possible? Example/Explanation

0 00 Not 0

Not 0 0Not 0 Not 0


There and Back

You and a friend decide to drive to Las Vegas, Nevada on Saturday over Labor Day weekend to go to a concert with some friends who live there. You figure you have to reach the vicinity of Las Vegas by 6 PM in order to meet your friends for dinner before the concert.

1. It's 574 miles from UNM to the Las Vegas strip. You'd like to stop for lunch and gas bout noon. What does your average velocity need to be?

2. It's almost all highway driving from here to Las Vegas. If you keep your speed approximately constant, what speed should your speedometer read while you are driving?

3. After you return to UNM, what is your displacement from the time you left to go to Las Vegas? What is the total distance traveled? What is your average speed and velocity?


Making a Motion Diagram

3


Examples of Motion Diagrams

8


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


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


Which Way?

• Which way is this object moving? • Is it speeding up or slowing down?• How can you tell?


Assume speed changes occur quickly compared to time scale=> will appear instantaneous

1.Slow then Fast

2.Fast, stop, Slow

3.Turnaround

Motion Diagram Examples


Here is a motion diagram of a car moving along a straight stretch of road:

Which of the following velocity-versus-time graphs matches this motion diagram?

Checking Understanding

A.

Slide 2-13

B. C. D.


Here is a motion diagram of a car moving along a straight stretch of road:

Which of the following velocity-versus-time graphs matches this motion diagram?

Slide 2-14

C.

Answer


Where’s the train?

A train is moving at a steady 30 m/s. At t = 0, the engine passes a signal light at x = 0. Without using any formulas, find the engine's position at t = 1s, 2s, and 3s.

Express your reasoning in words.


Where’s the train?

A train is moving at a steady 30 m/s. At t = 0, the engine passes a signal light at x = 0. Without using any formulas, find the engine's position at t = 1s, 2s, and 3s.

Express your reasoning in words.

EQUATION FROM GRAPH

EQUATION FROM AREA


A graph of velocity versus time for a hockey puck shot into a goal appears like so:

Which of the following position graphs matches the above velocity graph?

Checking Understanding

A. B. C. D.

Slide 2-21


A graph of velocity versus time for a hockey puck shot into a goal appears like so:

Which of the following position graphs matches the above velocity graph?

Answer

A. B. C. D.

Slide 2-22


Example ProblemA car moves along a straight stretch of road. The graph below shows the car’s position as a function of time.

At what point (or points) do the following conditions apply?

• The displacement is zero.

• The speed is zero.

• The speed is increasing.

• The speed is decreasing.

Slide 2-14


Acceleration

Acceleration is:

• The rate of change of velocity

• The slope of a velocity-versus-time graph

Slide 2-26


Particle Motion:

Slide 1-7

The picture above is made with a stroboscope (a light that flashes at regular time intervals) made at two frames of film per second, of a ball rolling along a track. The track has a 3.0-m-long sticky section.

a.Make a position-versus-time graph for the ball. Because you have data only at certain instants of time, your graph should consist of dots that are not connected together.

b.What is the change in the ball’s position from t = 0 s to t = 1.0 s?

c. What is the change in the ball’s position from t = 2.0 s to t = 4.0 s?

d. What is the ball’s velocity before reaching the sticky section?

e. What is the ball’s velocity after passing the sticky section?

f. Determine the ball’s acceleration on the sticky section of the track.


In each of the next four trials, you have to try to find a way to move such that you match the given representation and fill in the other two representations. (i.e. you are given a velocity vs. time graph and have to move to create the

same velocity vs. time graph)

Description of motion from Trial #10

Human Motion Demo - Trial 10

Slide 1-7

© 2010 pearson education, inc. week 3 day 2: topics slide 1-7 particle model general motion model...

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