1. 2. Write down an example of speed and an example of velocity.
Velocity Review
1. What is the difference between speed and velocity?
2. Write down an example of speed and an example of velocity.

2. Even More Practice
A plane is flying from Atlanta to San Diego at 520 mph west. It encounters wind from the jet stream moving at 30 mph east. What is the planes resultant velocity?
What about if the plane were headed east from San Diego to Atlanta instead?

3. Give an example of an object in freefall.
Bellringer
Give an example of an object in freefall.

4. 3.3 Acceleration and direction
Remember..a change in velocity occurs whenever there is a change in speed, direction, or both.

5. 3.3 Acceleration
Acceleration is the rate at which velocity changes. (How quickly an object changes speed or direction)

7. 3.3 Speed and acceleration
Speed and acceleration are not the same thing.
Acceleration is the change in speed divided by the change in time.

9. Acceleration Calculations
If you start from a standstill and are going 5 meters per second at the end of 5 seconds, what is your rate of acceleration?

10. More Practice
A plane passes over Point A with a velocity of 8,000 m/s north. Forty seconds later it passes over Point B at a velocity of 10,000 m/s north. What is the plane’s acceleration from A to B?
(remember to include units and direction in your answer!)

11. Explain why each of the following is an example of acceleration….
Increase in speed
Decrease in speed
Change in direction
A plane taking off
Stopping at a corner
Jogging on a track
Driving around a corner

12. 3.3 Acceleration and motion graphs
A speed vs. time graph is useful for showing how the speed of a moving object changes over time.
If the line on the graph is horizontal, then the car is moving at a constant speed.
There is no change in speed so there is no acceleration.

13. 3.3 Acceleration and motion graphs
Like velocity, acceleration can be positive or negative.
Positive acceleration adds more speed each second.
Speed is increasing at the same rate.

14. 3.3 Acceleration and motion graphs
Negative acceleration subtracts some speed each second, so things get slower.
People sometimes use the word deceleration to describe slowing down.
Speed is decreasing at the same rate.

15. Graphing Acceleration
Between which 2 points do you find:
Negative acceleration?
Positive acceleration?
Steady speed?

16. Try this one…
A coconut falls from the top of a tree and reaches a velocity of 19.6 m/s when it hits the ground. It takes 2 seconds to reach the ground. What is the coconut’s acceleration?
(remember to include units and direction in your answer)

17. Solution
a = (v2-v1) = t
What force is causing the coconut to fall downward?

18. Solution
a = (v2-v1) = t
What force is causing the coconut to fall downward?
GRAVITY

19. 3.3 Free fall
An object is in free fall if it is accelerating due to the force of gravity and no other forces are acting on it.
Objects in free fall on Earth accelerate downward.

20. 3.3 Free fall
Falling objects increase their speed by 9.8 m/s every second, or 9.8 m/s2
The letter “g” is used for acceleration due to gravity.

21. 3.3 Acceleration and direction
Acceleration occurs whenever there is a change in speed, direction, or both.

22. 3.3 Acceleration and direction
A car driving around a curve at a constant speed is accelerating because its direction is changing.

23. 3.3 Curved motion A soccer ball is an example of a projectile.
A projectile is an object that is moving forward AND is also under the influence of gravity.

24. 3.3 Curved motion Circular motion is another type of curved motion.
An object in circular motion has a velocity vector that constantly changes direction.

25. Section Review – page 73
3, 4, 5
7, 8, 9