Acceleration- Change in Velocity

• occurs when an object _____________________

•occurs when an object ______________ in speed.

• occurs when an object __________ in speed.

Types of acceleration

• Increasing speed– Example: Car speeds up at green light

• Decreasing speed– Example: Car slows down at stop light

• Changing Direction– Example: Car turns

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Question 1

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

_______________________________________

_______________________________________

Calculating Acceleration

Acceleration = Final speed – Initial speed Time

Calculating Acceleration

0 s 1 s 2 s 3 s 4 s

0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

Acceleration = 16m/s - 0m/s 4s

Acceleration = _______

Question 2

• A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

a = m/s – m/s s a = ____

a = __________

Graphing Acceleration

• Can use 2 kinds of graphs–Speed vs. time–Distance vs. time

Graphing Acceleration:Speed vs. Time Graphs

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d (

m/s

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Speed is increasing with time = accelerating

Line is straight = acceleration is constant

Graphing Acceleration:Speed vs. Time Graphs

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In Speed vs. Time graphs:Acceleration = Rise/Run = 4 m/s ÷ 2 s = ________

Run = 2 s

Rise = 4 m/s

Graphing Acceleration:Distance vs. Time Graphs

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Time (s)

Dis

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(m

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Curved line means the object is accelerating. Your speed is increasing. Remember slope = speed.

Question 3

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1)How is the speed of the car changing? (speeding up, slowing down, or staying the same) __________________________

2) What is this car’s acceleration? __________

Run = 3 s

Rise = -6 m/s

Question 4

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1) Which line(s) represents an object that is accelerating? ________________________________

2) Which line(s) show positive acceleration? ________________________________3) Which line(s) show negative acceleration? ________________________________4) Which line(s) show constant acceleration? _________________________________