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EXAMPLE:EXAMPLE: KingdaKingda KaKa Coaster: 0 – 128 mph in 3.5 seconds through hydraulic system & compressed air.Coaster: 0 – 128 mph in 3.5 seconds through hydraulic system & compressed air.

Jennifer Brown

Section 4.3

Acceleration –•The rate at which your speed (or velocity) changes.

•If your speed increases by 1 meter per second for each second, then your acceleration is 1 meter per second per second (m/s2).

Sections 4.1 - 4.3Jennifer Brown

Jennifer Brown

Sections 4.1 - 4.3

Can you have acceleration if you are travelling at constant speed?

• No: There is zero acceleration at constant speed because the speed does not change.

Jennifer Brown

Sections 4.1 - 4.3

Speed and acceleration are not the same thing.

You can be moving (constant speed), but have no acceleration (think cruise control).

Jennifer Brown

Sections 4.1 - 4.3

Acceleration describes how quickly speed changes.

Acceleration is the change in speed change in speed divided by the change in timechange in time.

Jennifer Brown

Sections 4.1 - 4.3

Jennifer Brown

Sections 4.1 - 4.3

An acceleration of 20 km/h/s means that the speed increases by 20 km/h each second.

The units for time in acceleration are often expressed as “seconds squared” and written as s2.

Jennifer Brown

Sections 4.1 - 4.3

The word “acceleration” is used for any change in speed, up or down.

Acceleration can be positive or negative, which makes it a what?•VECTOR!VECTOR!

Jennifer Brown

Sections 4.1 - 4.3

Positive acceleration adds more speed each second.

Things get faster. Speed increases

over time.

Jennifer Brown

Sections 4.1 - 4.3

Negative acceleration subtracts some speed each second.

Things get slower. People sometimes use

the word deceleration to describe slowing down.

Jennifer Brown

Sections 4.1 - 4.3

How do we solve problems dealing with acceleration? :

1) Calculate the acceleration of an airplane that starts at rest and reaches a speed of 45 m/s in 9 seconds?

•Answer: 5 m/s2

2) Calculate the acceleration of a car that slows from 50 m/s to 30 m/s in 10 seconds?

•Answer: -2 m/s2

Jennifer Brown

Sections 4.1 - 4.3