1. Opening Activity Compare and contrast the following:
Speed and velocity
Distance and displacement
Average speed and instantaneous speed
A cyclist must travel 800 km. How many days will the trip take if the cyclist travels 8 h/day at an average speed of 16 km/h?

2. 3.2 Acceleration pp 76-80 Essential Questions
How are time, velocity, and acceleration related?
How do I calculate the average acceleration of an object?
What is positive and negative acceleration and how are they different?

3. Acceleration, Speed, and Velocity p 76
When a car takes from a stop, the car’s velocity increases. It also accelerates.
Acceleration is the change in velocity divided by the time for the change to occur

4. Acceleration, Speed, and Velocity p 76
When a car slows down and stops, the car’s velocity decreases. It also accelerates (deceleration).

5. Changing Direction p 77
Acceleration occurs when an object changes its speed, its direction, or both.
We now have three terms that have magnitude (size) and direction; these are vectors. Name the other two vectors we have covered

6. Changing Direction p 77
Any time a moving object changes direction, its velocity changes and it is accelerating.

7. Calculating Acceleration
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊
Standard units = m/s2
If a = 1 m/s2, it means that its velocity (speed) is increasing 1 m/s every second.

8. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?

9. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = _____ vf = ______ Δt = _____

10. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = ______ Δt = _____

11. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = _____

12. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s

13. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s
𝒂= Δ𝒗 Δ𝒕

14. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊

15. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟖𝟎 𝒎 𝒔 − 𝟎 𝒎 𝒔 𝟐𝟎 𝒔

16. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟖𝟎 𝒎 𝒔 − 𝟎 𝒎 𝒔 𝟐𝟎 𝒔 = 𝟒𝟎 𝒎/𝒔 𝟐𝟎 𝒔

17. Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is the plane’s average acceleration?
vi = 0 m/s vf = 80 m/s Δt = 20 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟖𝟎 𝒎 𝒔 − 𝟎 𝒎 𝒔 𝟐𝟎 𝒔 = 𝟒𝟎 𝒎/𝒔 𝟐𝟎 𝒔 = 2.0 m/s2

18. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?

19. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?
vi = _____ vf = _____ Δt = _____

20. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?
vi = 3 m/s vf = 0 m/s Δt = 2 s

21. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?
vi = 3 m/s vf = 0 m/s Δt = 2 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊

22. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?
vi = 3 m/s vf = 0 m/s Δt = 2 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟎 𝒎 𝒔 − 𝟑 𝒎 𝒔 𝟐 𝒔

23. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboard’s average acceleration?
vi = 3 m/s vf = 0 m/s Δt = 2 s
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟎 𝒎 𝒔 − 𝟑 𝒎 𝒔 𝟐 𝒔 = −𝟑 𝒎/𝒔 𝟐 𝒔 = -1.5 m/s2

24. Opening Activity
It takes a car one minute (60 seconds) to go from a dead stop to a speed of 40 m/s. What is the average acceleration of the car?
A truck cruising at 50 m/s slams on its brakes to avoid a collision, stopping in 3.5 s. What is the acceleration of the truck

25. Opening Activity
It takes a car one minute (60 seconds) to go from a dead stop to a speed of 40 m/s. What is the average acceleration of the car?

26. Opening Activity
It takes a car one minute (60 seconds) to go from a dead stop to a speed of 40 m/s. What is the average acceleration of the car? t = 60s vi = 0 m/s vf = 40 m/s a = ???

27. Opening Activity
It takes a car one minute (60 seconds) to go from a dead stop to a speed of 40 m/s. What is the average acceleration of the car? t = 60s vi = 0 m/s vf = 40 m/s a = ??? = (vf – vi)/(tf – ti)=(40-0)/ = 0.67 m/s2

28. Opening Activity
A truck cruising at 50 m/s slams on its brakes to avoid a collision, stopping in 3.5 s. What is the acceleration of the truck?

29. Opening Activity
A truck cruising at 50 m/s slams on its brakes to avoid a collision, stopping in 3.5 s. What is the acceleration of the truck? t = 3.5s vi = 50 m/s vf = 0 m/s a = ???

30. Opening Activity
A truck cruising at 50 m/s slams on its brakes to avoid a collision, stopping in 3.5 s. What is the acceleration of the truck? t = 3.5s vi = 50 m/s vf = 0 m/s a = ??? = (vf – vi)/(tf – ti)=(0-50)/ = m/s2

31. Speed-Time Graphs – Calculating Positive Acceleration
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟖𝟎 𝒎 𝒔 − 𝟎 𝒎 𝒔 𝟐𝟎 𝒔 = 𝟒𝟎 𝒎/𝒔 𝟐𝟎 𝒔 = 2.0 m/s2

32. Speed-Time Graphs – Calculating Negative Acceleration
𝒂= Δ𝒗 Δ𝒕 = 𝒗𝒇 − 𝒗𝒊 𝒕𝒇 − 𝒕𝒊 = 𝟎 𝒎 𝒔 − 𝟑 𝒎 𝒔 𝟐 𝒔 = −𝟑 𝒎/𝒔 𝟐 𝒔 = -1.5 m/s2

33. 3.2 Homework
p (All classes)
p , (Honors)