AIM: How do we define, calculate and graph acceleration?

OBJ: Given notes and activity sheet SWBAT define, calculate and graph acceleration/deceleration with 70% accuracy

DN: Review Speed Lab’s Graphing Motion Pt. 3 (Note: 80cm = 0.8m; speed: m/s); Hand-in Speed Lab and SLQ Quiz scantron.

ACT: Introduction to Acceleration (notes)

Text, read p. 22-27

HW: Complete Acceleration Activity Sheet; Work on Third Quarter Review Sheets. Study for Interim Exam (Tuesday, March 31)

SPEED FORMULAInstantaneous Speed = distance = d

time t

Average Speed = final distance – initial distance

final time – initial time

Average Speed = df – di where: i = starting

tf – ti f = ending

How Can We Show Speed On A Graph?

Time (s)

Distance (m)

0 0

1 15

2 40

3 75

4 80

5 90

6 90

1) What was the average speed at 2 seconds?2) What was the average speed at 3 seconds?

3) What was the average speed at 6 seconds?4) What was the speed between 5 and 6

seconds?5) During which interval was speed the

highest?

ANSWER1) 40m – 0m =40 = 20 m/s

2s – 0s 2

2) 75 – 0 = 75 = 25 m/s

3 – 0 3

3) 90 -0 = 90 = 15 m/s

6 – 0 6

4) 90-90 = 0 = 0 m/s

6-5 1

5)Between 2 and 3; steepest slope

75 – 40 = 35 = 35 m/s

3-2 1

Acceleration

Acceleration: rate at which velocity changes (increasing speed, decreasing speed or changing direction)

Increasing Speed

Acceleration: object’s speed increases

Example: pitcher throws a ball

Bat hits a ball

Car passes another car

Biking down hill

Decreasing Speed

Deceleration: object’s slowing down; also called “negative acceleration”

Example: catching a soft ball

Car stops at a light

Boat stops pulling water skier.

Changing DirectionAcceleration: a constant speed with a change in direction.

Example: car accelerates around a gentle curve in a road or changing lanes

Runner accelerates around a curve on the track.

Circular motion: ferris wheel’s accelerate

Calculating Acceleration

Average Acceleration = Final speed-Initial speed

(straight line) Time

Units of Acceleration = m/s2, km/h2

Acceleration Example:

FREE FALL

Graphing AccelerationTo analyze the motion of an accelerating object, you can use:Speed vs. Time Graph1.slanted, straight line =

constant rate of acceleration

2. slope of the line = acceleration

Graphing AccelerationTo analyze the motion of an accelerating object, you can use:Distance vs. Time Graph1. curved line = acceleration

upward curved line = increasing speed

downward curved line = decreasing speed

2. slope of the line = speed