1. Unit 2: 1-D Constant Motion

2. Displacement
The change in position of an object is called displacement, Dd.
Example 1: I go running on the 3-mile jogging loop at Memorial park in Houston. I do three (3) laps. I am really tired. What is my total displacement?

3. Speed or Velocity? Speed and velocity are different quantities.
Speed is the rate distance covered of over time. Speed is a scalar quantity.
Velocity is the rate displacement traveled over time. Velocity is a vector quantity.
Speed and velocity differ when an object changes direction in its motion.

4. Different Types of Speed
Instantaneous Speed - the speed of an object at a given instant.
Average Speed – the speed of an object as it covers the total distance traveled over the total time interval.

5. Example 2
A brand new car has an odometer reading of 50 km after 45 minutes of travel. What is the average speed of the car in km/hr?
__ ∆ V = ∆d = df-di ∆t tf-ti

6. Example 3
According to Google Maps it will take 4.5 hours via I-45 if you travel by car from Sugarland to Dallas which is 418 km in total distance. Calculate the average speed in km/hr.

7. Example 4
What was the record time of Usain Bolt during the 100-m event in 2009 if he ran m/s?

8. Position vs. Time Graph
The d-t graph of a uniformly moving object is linear in shape.

9. Position vs. Time Graph
The slope of a linear graph is the rise (Dy) over the run (Dx).
The slope of an p-t graph describes the average velocity of object in motion.
For a p-t graph… d d d

10. When describing motion do 2 things:
Describe what the Y is doing
Describe what the slope is doing

12. Velocity vs. Time Graph
A velocity-time (v-t) graph plot of velocity as a function of time.
The v-t graph of a uniformly moving object is a horizontal line.
Velocity is constant!

13. Velocity vs. Time Graph
The v-t graph of an object moving at a non-uniform rate is a sloped line.
The velocity is changing at a constant rate.

14. Velocity vs. Time Graph
The slope of a v-t graph describes the rate of change in velocity over time.

15. Constant Velocity

16. Example 6
Describe the motion at each letter

17. Velocity vs. Time Graph
In the given v-t graph, the area under the graph is a rectangle.
area = l x w = v x Dt v x Dt = Dx (displacement)
The area under a v-t graph is equal to the displacement traveled over time.

18. Velocity vs. Time Graph
In the given v-t graph, the area under the graph is a triangle.
area = ½ x b x h = ½ x Dt x v = Dd (displacement)
The area under the v-t graph is still equal to the displacement traveled over time.

19. Example 7
What is the displacement of the object from sec?

20. Positive slope/above line = + position
Neg slope/below line =
- position

21. Example 8
What is the displacement of the object from 0-4 sec?