1. Complete TPFT Washer Demo 5.2
Displacement
Initial and final position
Path Distance

2. Motion
Movement is all around you. How can you tell something is moving?
Perceiving motion is instinctive —your eyes pay more attention to moving objects than to stationary ones.
When an object is in motion, its position changes along a path: (straight line, a circle, an arc, or a back and- forth vibration).
To simplify the concept of motion, we will first consider motion that takes place in one direction.
Position, Velocity & Acceleration Video

3. Who is observing matters!
Identify the object of interest AND the Observer
An observer in a spaceship describes the motion of the Sun differently than an observer standing on Earth.
The observer must be specified!
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4. Observational experiment
Different observers can describe the same process differently, including whether motion is even occurring.
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5. Linear motion
Linear motion is a model of motion that assumes that an object, considered as a point-like object, moves along a straight line.
A car moving along a straight highway can be modeled with linear motion; we simplify the car as a point, which is small compared to the length of the road.
A tire of the car cannot be modeled with linear motion.
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6. Picturing Motion Picturing Motion
A description of motion relates place and time
(where and when).
In the figure below, the car has moved from point A
to point B in a specific time period.

7. Picturing Motion Motion Diagram Particle Model
series of images showing the positions of a moving object at equal time intervals
Particle Model
simplified version of a motion diagram in which the object in motion is replaced by a series of single points. (remember…EQUAL TIME INTERVALS)

8. Lab
Gallean Ramp Experiment

9. Where and When?
The origin could be placed anywhere; in this example it is placed 5 m to the left of the tree.

10. Where and When?
You can indicate how far away an object is from the origin at a particular time by drawing and arrow from the origin to the object.

11. Where and When?
The arrow shown in the figure represents the runner’s position,
position is the separation between an object and the origin.

12. Where and When?
The length of the arrow represents distance the object is from the origin at a particular time.
The arrow shows direction from the origin at a particular time.

13. Where and When?
A position 9 m to the left of the tree (or 5 m left of the origin) would be a negative position.
“positive” and “negative” tell us direction from the origin

14. Time Intervals and Displacements
The difference between the initial and the final times is called the time interval.

15. Time Intervals and Displacements
displacement is a vector with its tail at the origin of a coordinate system and its tip at the place where the object is located at that time.

16. Time Intervals and Displacements
The difference between the initial and the final position is called the displacement.
The length of the arrow represents the distance the runner moved during the time interval, while the direction the arrow points indicates the direction of the displacement.

17. Position:
Separation between object and the origin
A vector

18. Path travled (Distance traveled):
the total length of the path followed from starting point to end point and may be greater than or equal to the displacement
Magnitude (how much) only
Scalar

19. Displacement: Final position minus initial position
measures only the net change in position from starting point to end point.
Change in position
It’s a Vector

20. How Fast?
Average velocity is defined as the change in position, divided by the time during which the change occurred.

21. Velocity Patterns found from motion diagrams
The spacing of the dots allows us to visualize motion.
When the object travels without speeding up or slowing down, the dots are evenly spaced.
When the object slows down, the dots get closer together.
When the object moves faster and faster, the dots get farther apart.
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22. Finding velocity change arrows
Consider two adjacent velocity vectors, in this example at points 2 and 3.
Find which vector would need to be added to the velocity corresponding to point 2 to get the velocity corresponding to point 3.
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23. Speed vs. Velocity Speed: magnitude of velocity
Scalar quantity no direction
Absolute value of “slope” of a position-time graph
Velocity: has both magnitude and direction
vector quantity
+ velocity + slope moving in the positive direction, its displacement is positive
- velocity - slope moving in the negative direction, its displacement is negative

24. Conceptual Exercise 1.1
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