1. Distance vs. Displacement Speed vs. Velocity
Unit A: Kinematics
Distance vs. Displacement
Speed vs. Velocity

2. Definitions (see handout).
Definitions (see handout)
Kinematics: is the study of how objects move.
Origin: a reference point (where we start).
Position: The straight – line distance between the origin and an object’s location; includes magnitude and direction.
Scalar quantities or scalars: are quantities that describe magnitude (size or amount) but not direction.
Ex. Medicine Hat is a 166km from Lethbridge.
Vector quantities or vectors: are quantities that describe magnitude as well as direction.
Medicine Hat is 166km East from Lethbridge.

3. Definitions (see handout)
Distance is a scalar quantity that describes the length of a path between two points or locations.
the symbol for distance is in meters
Displacement is a vector quantity that describes the straight-line distance from one point to another as well as the direction.
the symbol for displacement is in meters

4. Calculating Distance & Displacement
To calculate DISTANCE, simply add together all of the distances. Since distance is a scalar quantity there is not need to consider direction.
Ex. A student ran 50m E, 20m S, 35m W and 25m N. Calculate the distance the student ran.
130m

5. Calculating Displacement
DIRECTION MATTERS!!!
The following are direction conventions in physics:
Similar to a number line, right is +, left is –
East is +, West is –
North is +, South is –
Up is +, down is –
Total displacement of one object moving several different displacements is the vector sum of the displacements. It is where you are from your starting point.

6. Calculating TOTAL Displacement
Ex. A student walks 23m N, turns around and walks 33m S. What is the student’s total displacement?

7. Calculating CHANGE IN displacement
Ex. Mitch walks 4.3 m north of our classroom and Kelsey walks 3.7 m south of our classroom. What is the displacement from Mitch to Kelsey?
We are measuring from Mitch to Kelsey; so Mitch is and Kelsey is

8. Speed vs. Velocity
Speed: is the change in distance over a change in time. Speed does not take into account the direction the object is moving

9. Speed vs. Velocity
Velocity: is the change in displacement over time. Velocity takes direction into account!
The direction can be positive (to the right) or negative (to the left). Moving to a more positive direction is positive velocity and moving to a less positive direction is negative velocity.
Scalar quantities are: distance and speed.
Vector quantities are: displacement and velocity (denoted with ).

10. More definitions… (see handout)
Instantaneous velocity: Velocity of an object at a specific time.
Average Speed: The average speed of an entire trip. Found by dividing the total distance traveled by the total time traveled.
Average velocity: The average velocity of an entire trip. Found by dividing the displacement by the total time.
Constant velocity: Average velocity is the same for all time intervals.
Relative velocity: The velocity of an object depends on the frame of reference of the observer. If the observer moves, the velocity of the object may change.

11. Sample Problem
Ex. A passenger is walking on the deck of a ship at 2m/s and the ship is moving at 10m/s.
-Stationary observer on the ship sees the passenger moving at 2m/s.
-Stationary observer on the land sees the passenger moving at12m/s.

12. Sample Problem
Ex. Find the velocity of a car that took 100s to go from the 12km marker on a road to the 10km.

13. Homework
pg. 1 #1-3
pg. 2 #1-5
pg.5 #10-12