1. Chapter 3
Describing Motion

2. 3.1 Picturing Motion Motion Diagrams The Particle Model
A series of images of a moving object that records its position after equal time intervals.
The Particle Model
Replacing the object with a single point.

3. Mini-lab
Using the ticker-tape timer, determine the constant speed you are able to pull the tape.
Repeat the lab but this time slowly increase the speed with which you pull the tape. What do we call this type of motion?
Plot the distance from the starting point to every sixth dot on the tape (1/10 of a second for each sixth dot).

4. Review Answer the following questions in your lab book.
1. What did you notice about the shape of the graphs?
2. Why were they not an exact fit to the line generated?
3. Describe how we could use this to model real life situations?
Compare your answers with your groups’ and whiteboard group consensus.

5. 3.2 Where and When Coordinate systems Vectors and Scalars
Tells you where the zero point is located.
Vectors and Scalars
Something that only tells you the magnitude is a scalar quantity.
A vector has both magnitude and direction

6. Time Intervals and Displacements
Displacement defines both the distance and direction between two positions and is therefore a vector.
∆t is the time interval (t1 – t0)
∆d is the change in displacement (d1 – d0)

8. 3.3 Velocity and Acceleration
Average velocity v is the change in position divided by the time it took to make the change.
v ≡ ∆d/ ∆t = d1 – d0 / t1 – t0
Instantaneous velocity
The velocity at any given point in time.
Average velocity motion diagrams

9. Acceleration
An object whose velocity is changing is said to be accelerating.
Average acceleration
a ≡ ∆v/ ∆t = v1 – v0 / t1 – t0

10. PSS
1. Sketch the problem. Establish a coordinate system and add it to your sketch. Reread the problem and make a list of unique symbols to represent each of the variables that are given or known. Decide which quantities are unknown and give them symbols. Create a physical model. Use this as a motion diagram.

11. 2. Calculate your answer. Use the physical model as a guide to the equations and graphs you will need.
3. Check your answer. Did you answer the question? Does the answer appear reasonable?