Chapter 4.3 Acceleration PowerPoint

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Jennifer Brown
Section 4.3

http://vimeo.com/609333
EXAMPLE:

Kingda Ka Coaster: 0 – 128 mph in 3.5
seconds through hydraulic system &
compressed air.
Jennifer Brown
Sections 4.1 - 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).
Jennifer Brown
Sections 4.1 - 4.3
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
divided by the change 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!
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
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