ACCELERATION

Changing Speeds

Not all objects move at a constant speed.

• Some objects speed up

• Some objects slow down

What is acceleration?Acceleration is a change in the

speed of an object.

• Speeding up acceleration

• Slowing down is also acceleration – (more commonly called “deceleration”)

What is acceleration?Constant Speed

Accelerating (speeding up)

Calculating Acceleration:

Calculating Acceleration:

• You must know its beginning speed V1

• You must know its ending speed V2

• You must also know how much time it took to change the speeds (from start to finish)

Calculating Acceleration:• Acceleration is the change in speed

divided by the time it took for the speed to change

so ….Acceleration = (Change in Speed) ÷ time

How do I find the change in speed?

To find the amount of change in anything:

Ending Amount - Beginning Amount

To find the change in Speed:

Final Speed - Beginning Speed

Acceleration Equation:

• A = acceleration (it has units of m/s2)• t = time (s)

Because there are two speeds:• Beginning Speed V1• Final Speed V2

A = (V2 – V1)t

Calculating Acceleration:• Acceleration is the change in speed over time

so ….

Acceleration = (Change in Speed) ÷ time

A = (v2 – v1)

t

Determining V1 and V2:A car with a speed of 10 m/s goes faster for 6 seconds until it reaches a new speed of 24 m/s. What acceleration does it show?

V1

V2

A bike with a speed of 4 m/s goes faster for 8 seconds until it reaches a new speed of 16 m/s. What acceleration does it show?

V1

V2

t

t

Example:A car with a speed of 10 m/s goes faster for 6 seconds until it reaches a new speed of 24 m/s. What acceleration does it show?

Given Unknown Equation Solution

V1 = 10 m/st = 6 s A = ? A = (v2-v1)

t

A = (V2 - V1) t

A = (24 – 10) = 14 6 6

A = 2.3 m/s2Scientific

Units

V2 = 24 m/s

V1

V2

Example #2:A bike with a speed of 4 m/s goes faster for 8 seconds until it reaches a new speed of 16 m/s. What acceleration does it show?

Given Unknown Equation Solution

V1 = 4 m/s

t = 8 s A = ? A = (V2-V1) t

A = (V2 - V1) t

A = (16 – 4) = 12 8 8

A = 1.5 m/s2Scientific

Units

V2 = 16 m/s

Online Acceleration Activities:

Online movies on acceleration:• Brainpop video• http://www.kidsknowit.com/interactive-educational-movies/f

ree-online-movies.php?movie=acceleration

Online acceleration activities:• moving-man activity• Acceleration Maze Game