Download Acceleration

Acceleration
This topic can be found in your textbook on pp. 48-52
Vocabulary:
• acceleration
• rate
“In the Car” (1963)
Roy Lichtenstein
What do you think?
 What is acceleration?
 Write down your own definition from your
experience.
 Share your answer with your neighbor and
see if you can refine your definition.
 Now share your refined answer with
another group and see if you can refine it
even more.
What do you think?

Based on your definition of acceleration, are any
of the following cars accelerating?
a. A car shortly after a stoplight turns green
b. A car approaching a red light
c. A car with the cruise control set at 80 km/h
d. A car turning a curve at a constant speed
e. A car crashing into a tree
f. A car rolling down a hill without brakes
 Do you think you need to modify your definition
after thinking about any of these situations? Why
or why not?
Acceleration
 Definition: The rate of change of velocity.
 How does this compare to your definition?
 (BTW: What does “rate” mean again?)
What do you think?
 What evidence do you have that the car below
is accelerating? (Each picture was taken at 1
second intervals.)
0s 1s
2s
3s
4s
What do you think?
 Because the car has travelled a greater distance
each second, it must have a greater velocity
each second. By definition it is accelerating
because the car is changing velocity.
0s
1s
2s
3s
Acceleration due to Gravity
 Once again you can see
the effects of
acceleration using stop
motion photography.
Acceleration Mathematically
 Since acceleration is the rate of change in velocity,
acceleration can be calculated using the following
equation:
∆𝑣
𝑎=
∆𝑡
or
𝑣𝑓 − 𝑣𝑖
𝑎=
∆𝑡
SI Units:
𝑚/𝑠
𝑠
or m/s2
Important points:
 Acceleration is a vector (it has both magnitude
and direction), so…
 Speeding up is acceleration
 Slowing down is acceleration
 Changing direction is acceleration
Think about the following scenarios. What will
the sign of the acceleration be?
Initial Motion
Change in Motion
Sign of
Acceleration
Moving forward
(+ direction)
Speeds up
positive
Moving forward
(+ direction)
Slows down
negative
Moving backward
(- direction)
Speeds up
negative
Moving backward
(- direction)
Slows down
positive
Moving forward
(+ direction)
No change in motion
no acceleration
Math Practice
 Find the acceleration of an amusement park
ride that falls from rest and reaches a velocity
of 23 m/s downward in 3.0 s.
 Answer: -7.7 m/s2
Math Practice
 If a car traveling at 5.67 m/s speeds up over
15.0 s with a constant acceleration of 2.3 m/s2,
what is the car’s final acceleration?
Acceleration Summary
Measurement
Symbol
SI Unit
acceleration
a
m/s2
Equation Summary
𝑣𝑓 − 𝑣𝑖
𝑎=
∆𝑡