1. Acceleration

2. Acceleration Acceleration = speeding up
Acceleration – the rate at which velocity changes
Can be an:
Increase in speed
Decrease in speed
Change in direction

3. Types of acceleration Increasing speed Decreasing speed
Example: Car speeds up at green light
Decreasing speed
Example: Car slows down at stop light
Changing Direction
Example: Car takes turn (can be at constant speed)
screeeeech

4. Question
How can a car be accelerating if its speed is a constant 65 km/h?
If it is changing directions it is accelerating

5. Calculating Acceleration
If an object is moving in a straight line
Units of acceleration:
Distance/ time = distance/time2
time
m/s2

6. Calculating Acceleration
0 s
1 s
2 s
3 s
4 s
0 m/s
4 m/s
8 m/s
12 m/s
16 m/s

7. Question
A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

8. Graphing Acceleration
Can use 2 kinds of graphs
Speed vs. time
Position vs. time

9. Graphing Acceleration: Speed vs. Time Graphs
Speed is increasing with time = accelerating
Line is straight = acceleration is constant

10. Graphing Acceleration: Speed vs. Time Graphs
Rise = 4 m/s
Run = 2 s
In Speed vs. Time graphs:
Acceleration = Rise/Run
= 4 m/s ÷ 2 s = 2 m/s2

11. Graphing Acceleration: Position vs. Time Graphs
On Position vs. Time graphs a curved line means the object is accelerating.
Curved line also means your speed is increasing. Remember slope = speed.

12. Question Run = 3 s Rise = -6 m/s
Above is a graph showing the speed of a car over time.
1) How is the speed of the car changing (speeding up,
Slowing down, or staying the same)?
2) What is this car’s acceleration?
The car is slowing down
Acceleration = rise/run = -6m/s ÷3s = -2 m/s2

13. curved line = accelerating, straight line = constant speed
Question:
The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down
Remember: in position vs. time graphs:
curved line = accelerating,
straight line = constant speed
Which line represents an object that is accelerating?

14. Question: Hard one

15. Free fall
The constant acceleration of an object moving only under the force of gravity
If there was no air, all objects would fall at the same speed regardless of the masses

16. Acceleration due to gravitational force
d = vit + ½gt2
If vi = 0, then d = ½ gt2
g = acceleration due to the force of gravity
= 9.8 m/s2
= 10 m/s2

17. Free fall After 1 second falling: v= 10 m/s
After 2 seconds: v = 20 m/s
After 3 seconds: v = 30 m/s

18. Falling Air resistance will increase as it falls faster
An upward force on the object
Eventually gravity will balance with air resistance
Reaches terminal velocity - highest speed reached by a falling object.

19. Bozeman videos

20. Questions
Answer the following questions and me your answers. )
1. How can a car accelerate without the speedometer changing?
2. What does the slope of a velocity vs time graph give you?
3. What is the value of the acceleration due to the force of gravity on Earth?
4. What is the color of the object that is rolled across the table by Mr. Andersen?