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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 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?

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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?

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

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

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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

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

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Calculating Acceleration

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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 planes average acceleration?

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v i = _____ v f = ______ t = _____

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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 planes average acceleration? v i = 0 m/s v f = ______ t = _____

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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 planes average acceleration? v i = 0 m/s v f = 80 m/s t = _____

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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 planes average acceleration? v i = 0 m/s v f = 80 m/s t = 20 s

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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 skateboards average acceleration?

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v i = _____ v f = _____ t = _____

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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 skateboards average acceleration? v i = 3 m/s v f = 0 m/s t = 2 s

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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

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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?

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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 = ???

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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

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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?

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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 = ???

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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 = -14.29 m/s 2

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Speed-Time Graphs Calculating Positive Acceleration

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Speed-Time Graphs Calculating Negative Acceleration

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3.2 Homework p 80 1-7 (All classes) p 880 26-28, 30-32 (Honors)