1. Describing Motion: Kinematics in One Dimension
Chapter 2
Describing Motion: Kinematics in One Dimension

2. Today: Units of Chapter 2
Reference Frames
Displacement and Distance
Average Velocity
Instantaneous Velocity (optional for us)

3. 2-1 Reference Frames
Any measurement of position, distance, or speed must be made with respect to a reference frame.
It can be anything: a street corner, the Earth, a point…
example: a person is walking down the aisle (5m/s) of a moving train (20 m/s).
ex:
moving frames (
Earth-Sun (
we will use systems of coordinates most of the times!

4. 2-1 Displacement and Distance distance displacement.
Displacement (blue line) = how far the object is from its starting point, regardless of how it got there. VECTOR!
Distance traveled (dashed line) = measured along the actual path. SCALAR (= just a number)!

5. Vectors = mathematical models which have: Magnitude (= value) – unique
Direction – unique
for us, in one dimension, the direction could be the sign, + is to the right, - is to the left
Origin – not unique ( it could be changed without changing the vector)

6. 2-1 Displacement (VECTOR)
The displacement is written:
Right:
Displacement is positive.
Left:
Displacement is negative.

7. 2-2 Average Velocity
Speed: how far an object travels in a given time interval (m/s)
Velocity includes directional information (m/s):
In our first example, if the elapsed time is 10 seconds, calculate speed and velocity:

8. 2-3 Instantaneous Velocity
If time permits, discuss this concept on the board.
If the moving object does not turn around,
displacement will have the same value as the distance!
and
are virtually the same formula…

9. Fly Puzzle