1. Notes 9-3 Acceleration

2. Rate velocity changes with time Vector quantity In science, acceleration refers to increasing speed, decreasing speed, or changing direction Decreasing speed = deceleration

3. Calculating Acceleration To determine the acceleration of an object, you must calculate its change in velocity per unit of time. Acceleration = Final Velocity – Initial Velocity Time Chapter 9 Motion and Energy

4. Let’s Try a Problem Calculate the plane’s acceleration in the first 5 seconds of motion. A= V f – V i time A = 40 m/s – 0 m/s 5 s A = 8 m/s 2

5. Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Read and Understand What information have you been given? Initial velocity = 4 m/s Final velocity = 22 m/s Time = 3 s Chapter 9 Motion and Energy

6. Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Plan and Solve What quantity are you trying to calculate? The acceleration of the roller-coaster car = __ What formula contains the given quantities and the unknown quantity? Acceleration = (Final velocity - Initial velocity)/Time Perform the calculation. Acceleration = (22 m/s - 4 m/s)/3 s = 18 m/s/3 s Acceleration = 6 m/s 2 The acceleration is 6 m/s 2 down the slope. Chapter 9 Motion and Energy

7. Calculating Acceleration As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Look Back and Check Does your answer make sense? The answer is reasonable. If the car’s velocity increases by 6 m/s each second, its velocity will be 10 m/s after 1 second, 16 m/s after 2 seconds, and 22 m/s after 3 seconds. Chapter 9 Motion and Energy

8. Calculating Acceleration Practice Problem A falling raindrop accelerates from 10 m/s to 30 m/s in 2 seconds. What is the raindrop’s acceleration? (30 m/s - 10 m/s) ÷ 2 seconds = 10 m/s 2 Chapter 9 Motion and Energy

9. Calculating Acceleration Practice Problem A certain car can accelerate from rest to 27 m/s in 9 seconds. Find the car’s acceleration. (27 m/s - 0 m/s) ÷ 9 s = 27 m/s ÷ 9 s = 3 m/s 2 Chapter 9 Motion and Energy

10. Graphing Acceleration You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object. Chapter 9 Motion and Energy

11. Mr. Edmonds!! http://youtu.be/4CWlNoNpXCc