1. Unit B 1.3 Acceleration

2. Types of Acceleration Positive Acceleration Occurs in Two Ways
When an object’s velocity is increasing in a positive direction.
When an object’s velocity is decreasing in a negative direction
Negative Acceleration Occurs in Two Ways
When an object’s velocity is decreasing in a positive direction
When an object’s velocity in increasing in a negative direction

3. Using Formulas and Graphs to Analyze Accelerated Motion
Acceleration = change in velocity
time interval
a = vf - vi ∆t

4. Example
A racing car accelerates from rest to a speed of 200km/h (55.6m/s) [E] in 6.00s. What is the acceleration of the car.

5. Solution a = vf - vi ∆t a = 55.6m/s – 0.00m/s 6.00s = 9.27m/s2
The car’s velocity is increasing at the rate of 9.27m/s2 [E] (This is positive acceleration)

6. Plotting a Position-Time Graph
Positive acceleration, slope is increasing.
Negative acceleration, slope is decreasing.

7. Example Interpret the position-time graph for the data in the table
Using the graph, identify the motion occurring in the time intervals given below.
Between 0.0s and 3.0s
Between 3.0s and 6.0s
Between 6.0s and 8.0s
Time (s)
Position (m) [E]
0.0
1.0
10.0
2.0
40.0
3.0
90.0
4.0
140.0
5.0
190.0
6.0
240.0
7.0
270.0
8.0
290.0

8. Solution

9. The straight line shows uniform motion [E].
The curve has an increasing slope so it shows positive acceleration [E].
The straight line shows uniform motion [E].
The curve has a decreasing slope so it shows negative acceleration [E].
Practice Problem 16 p. 149

10. Plotting a Velocity-Time Graph
The slope of a velocity-time graph indicates the acceleration of the object.
slope = rise = ∆v
run ∆t

11. Example Draw a velocity-time graph for the data shown in the table
Using the graph identify the motion occurring at the time intervals given below
Between 0.0s and 3.0s
Between 3.0s and 5.0s
Between 5.0s and 8.0s
Time (s)
Velocity (m/s) [E]
0.0
1.0
2.0
4.0
3.0
6.0
5.0
7.0
8.0

12. Solution

13. The straight horizontal line shows uniform motion [E].
The straight line with a positive slope shows that the object was travelling with positive acceleration [E].
The straight horizontal line shows uniform motion [E].
The straight line with a negative slope shows negative acceleration [E].
Practice Problem 17 p. 153

14. CONVERTING km/h to m/s

15. Homework: read Science 10 p. 146 – 154
Practice Problems pg
Check and Reflect 1-10 pg 154