1. Homework Check
300km
364km
250km/hr
120km/hr
2km/m
900km/hr
5km/m

2. Acceleration
In Science, acceleration is defined as the rate at which velocity changes.
Acceleration occurs whenever direction and/or speed changes.
An increase in velocity is positive acceleration
A decrease in velocity is negative acceleration, or deceleration.
The faster the velocity changes, the greater the acceleration is.

3. Acceleration
To calculate average acceleration, use the following formula:
average acceleration = final velocity – initial velocity
time it takes to change velocity
The units on acceleration are meters per second per second (m/s/s) or meters per second squared (m/s2)

4. Acceleration
When graphing acceleration, velocity is on the y-axis and time is on the x-axis
When velocity is increasing on the graph, your acceleration is positive. When velocity is decreasing on a graph the acceleration is negative.
An object traveling in a circle is always changing direction. This means the velocity is always changing.
Centripetal acceleration occurs with circular motion.

5. Acceleration and Velocity-Time Graphs

6. Acceleration
Acceleration is a change in velocity divided by the time it takes for the change to happen.
Acceleration can be positive (speeding up) or negative (slowing down).

7. Practice Problems
Maria is jogging. She speeds up from 2 m/s to 8 m/s in 6 seconds. What is her acceleration?

8. Practice Problems
2. Sarah is driving when she sees a stoplight ahead. She slows down from 30 m/s to 10 m/s in 4 seconds. What is her acceleration?

9. Practice Problems
3. Tyler is running a race. Near the end, she speeds up, increasing her speed from 7 m/s to 13 m/s in 12 seconds. What is her acceleration?

10. Practice Problems
4. Kris is riding a bike. He slows down from 18 m/s to 9 m/s in 3 seconds. What is his acceleration?

11. Velocity-Time Graphs

12. Interpreting points from v-t graphs
Each point has y-coordinate and x- coordinate.
Y-coordinate tells you the velocity (speed) of the object at that point.
X-coordinate tells you the total time that has passed since object started moving.
Point B: (4, 8)
x = 4 s
y = 8 m/s

13. Practice
At point C, what is the object’s speed, and how much time has passed?
After 2 seconds, what was the object’s speed?
How many seconds did it take for the object to reach a speed of 6 m/s?
At point D, what is the object’s speed?

14. Calculating acceleration from v-t graphs
To find object’s acceleration during an interval:
Find the change in speed (y2 – y1)
Find the change in time (x2 – x1)
Divide change in speed by change in time

15. Example
Acceleration from point A to point B:

16. Practice
What was the acceleration from O to A?

17. Practice
What was the acceleration from A to B?

18. Practice
What was the acceleration from B to C?

19. Practice
What was the acceleration from D to E?

20. Independent practice time!

21. Practice
What was the acceleration from O to A?

22. Practice
2. What was the acceleration from A to B?

23. Practice
3. What was the acceleration from B to C?

24. Practice
4. What was the acceleration from D to E?

25. Acceleration
Acceleration is a change in velocity divided by the time it takes for the change to happen.
Acceleration can be positive (speeding up) or negative (slowing down).

26. Example
Acceleration from point A to point B: