Acceleration!Acceleration!

Chapter 9 Section 3Chapter 9 Section 3

AccelerationAccelerationLet’s Review: What is Speed? Velocity? Let’s Review: What is Speed? Velocity?

What is a Vector?What is a Vector?

AccelerationAcceleration: RATE at which : RATE at which velocity velocity changeschanges

Refers to INCREASING speed, Refers to INCREASING speed, DECREASING speed, or DECREASING speed, or CHANGING directionCHANGING direction..

Is Acceleration a Vector?Is Acceleration a Vector?

A softball accelerates when it is thrown, A softball accelerates when it is thrown, hit, or caught. What change in motion hit, or caught. What change in motion

occurs in each example?occurs in each example?

Thrown- ball accelerates as it is thrownThrown- ball accelerates as it is thrown

Hit- ball changes directionHit- ball changes direction

Caught- ball decelerates (negative Caught- ball decelerates (negative acceleration)acceleration)

How can a car be accelerating if its speed How can a car be accelerating if its speed is constant at 65 km/h?is constant at 65 km/h?

The arrows are larger as the plane increases speed or accelerates…the arrows represent the vector quantity.

BRAIN BREAK!BRAIN BREAK!Acceleration is like…Acceleration is like…

Because…Because…

Now, let’s play Gotcha!

Calculating Calculating AccelerationAcceleration

Final Velocity-Beginning Final Velocity-Beginning VelocityVelocity

TimeTime

Fv-Bvt

Beginning Velocity

Final Velocity

Time

a =

ExampleExample::As a roller coaster starts down a slope, its As a roller coaster starts down a slope, its

velocity is 4 m/s. But 3 seconds later, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. velocity is 22 m/s in the same direction.

What is its acceleration?What is its acceleration?Initial Velocity: 4 m/sInitial Velocity: 4 m/sFinal Velocity: 22 m/sFinal Velocity: 22 m/s

Time: 3 sTime: 3 s

Final Velocity – Initial Velocity/ TimeFinal Velocity – Initial Velocity/ Time22 m/s – 4 m/s22 m/s – 4 m/s

3 s3 s

18 m/s18 m/s = 6 m/s/s or = 6 m/s/s or 6 m/s26 m/s23 s3 s

Graphing AccelerationGraphing Acceleration Speed vs. Time GraphSpeed vs. Time Graph Upward means speed Upward means speed

is increasingis increasing

Line is straight means Line is straight means acceleration is acceleration is constantconstant

A horizontal line (flat) A horizontal line (flat) would mean that the would mean that the object is moving at a object is moving at a constantconstant speed. speed.

Slope on a speed vs. Slope on a speed vs. time graph time graph represents represents accelerationacceleration

Distance vs. Time GraphDistance vs. Time Graph Curved line means Curved line means

that the objects is that the objects is accelerating accelerating (nonlinear).(nonlinear).

During each second, During each second, the object traveled a the object traveled a greater distance than greater distance than the second before.the second before.

Slope is speed and Slope is speed and since slope is getting since slope is getting steeper and steeper, steeper and steeper, you can conclude that you can conclude that speed is also speed is also increasing…or that the increasing…or that the object is accelerating. object is accelerating.

THE END!