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Opening Activity 1.Compare and contrast the following: –Speed and velocity –Distance and displacement –Average speed and instantaneous speed 2.A cyclist.

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Presentation on theme: "Opening Activity 1.Compare and contrast the following: –Speed and velocity –Distance and displacement –Average speed and instantaneous speed 2.A cyclist."— Presentation transcript:

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2 Opening Activity 1.Compare and contrast the following: –Speed and velocity –Distance and displacement –Average speed and instantaneous speed 2.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?

3 3.2 Acceleration pp 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?

4 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

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

6 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

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

8 Calculating 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?

10 v i = _____ v f = ______ 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? v i = 0 m/s v f = ______ 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? v i = 0 m/s v f = 80 m/s Δt = _____

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? v i = 0 m/s v f = 80 m/s Δt = 20 s

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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?

20 v i = _____ v f = _____ Δt = _____

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? v i = 3 m/s v f = 0 m/s Δt = 2 s

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25 Opening Activity 1.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? 2.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

26 Opening Activity 1.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?

27 Opening Activity 1.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 v i = 0 m/s v f = 40 m/s a = ???

28 Opening Activity 1.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 v i = 0 m/s v f = 40 m/s a = ??? = (v f – v i )/(t f – t i )=(40-0)/60 = 0.67 m/s 2

29 Opening Activity 2.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?

30 Opening Activity 2.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 v i = 50 m/s v f = 0 m/s a = ???

31 Opening Activity 2.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 v i = 50 m/s v f = 0 m/s a = ??? = (v f – v i )/(t f – t i )=(0-50)/3.5 = m/s 2

32 Speed-Time Graphs – Calculating Positive Acceleration

33 Speed-Time Graphs – Calculating Negative Acceleration

34 3.2 Homework p (All classes) p , (Honors)


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