1. How do you calculate acceleration?

2. How can we make this balloon move along the string?
Anticipatory Set
How can we make this balloon move along the string?

3. California Standards
Science Standard 8.1.e: Students know changes in velocity may be due to changes in speed, direction, or both.
Science Standard 8.1.f: Students know how to interpret graphs of position versus time and graphs of speed versus time for motion in a single direction.

4. Input
acceleration: the rate at which velocity changes with time.

5. Input & Modeling Changing Velocity
In science, acceleration refers to increasing speed, decreasing speed, or changing direction.
Just as objects can speed up, they can also slow down. This change in speed is sometimes called deceleration, or negative acceleration.
An object that is traveling at a constant speed can be accelerating if it is changing direction.

6. Input & Modeling Changing Velocity
To determine the acceleration of an object, you must calculate its change in velocity per unit of time.
Acceleration = Final Velocity – Initial Velocity
Time

7. Calculating Acceleration
Input & Modeling
Calculating Acceleration
To determine the acceleration of an object, you must calculate its change in velocity per unit of time.

8. 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

9. 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/s2
The acceleration is 6 m/s2 down the slope .

10. 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.

11. 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?
Acceleration = (Final velocity - Initial velocity)/Time
(30 m/s - 10 m/s) ÷ 2 seconds = 10 m/s2

12. Calculating Acceleration
Practice Problem
A certain car can accelerate from rest to 27 m/s in 9 seconds. Find the car’s acceleration.
Acceleration = (Final velocity - Initial velocity)/Time
(27 m/s - 0 m/s) ÷ 9 s = 27 m/s ÷ 9 s = 3 m/s2

13. Graphing Acceleration
Input & Modeling
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.

14. HOMEWORK CONNECTION Read pages 350-355 in your Science textbook.
Complete the Section 9-3 Review & Reinforce
Write a detailed SUMMARY of the section and complete the UNANSWERED QUESTIONS section of your notes.
Choose two of the remaining Depth & Complexity ICONS in your notes and explain how they relate to this section.