9-3: AccelerationHow do you calculate acceleration?

Anticipatory Set

How can we make this balloon move along the string?

California StandardsScience 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.

Inputacceleration: the rate at which velocity

changes with time.

Input & ModelingChanging 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.

Input & ModelingChanging 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

Input & ModelingCalculating Acceleration

To determine the acceleration of an object, you must calculate its change in velocity per unit of time.

Calculating AccelerationAs 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

Calculating AccelerationAs 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)/TimePerform the calculation.

Acceleration = (22 m/s - 4 m/s)/3 s = 18 m/s/3 sAcceleration = 6 m/s2

The acceleration is 6 m/s2 down the slope .

Calculating AccelerationAs 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.

Calculating AccelerationPractice 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

Calculating AccelerationPractice 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

Input & ModelingGraphing Acceleration

You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object.

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.