1. zoom zoom
Acceleration

2. Acceleration Terms
Acceleration (a)– the rate of change of velocity (can be +, -, or centripetal)
Deceleration– only negative acceleration (slowing down)
Centripetal Acceleration– acceleration that occurs when changing direction (turning)
Freefall– objects falling due to gravity
Force is what you feel when you accelerate

3. 3 ways to accelerate
Since acceleration is a change in velocity and velocity has 2 parts
We can accelerate by
Changes in speed
Speed up (+ acceleration)
Slow down (- acceleration)
Changing Direction
Turning
Changing both speed and direction

4. Your speedometer – the key to accel
We don’t see acceleration of an object well with our eyes
But if we look at a speedometer we can see speed change.
Acceleration is a picture of what your speedometer is doing

5. Acceleration is a pic of your Speedo
Slow Acceleration
Fast(er) Acceleration
Acceleration is a pic of your Speedo

6. The Acceleration Graph Setup
The Variables
The Graph
Speed ( or velocity)is the dependent variable
Time is the independent variable
Graph setup = Formula
Speed
Dsp a= Dt
Time
The Acceleration Graph Setup

7. Acceleration& Slope (quick version)
Acceleration(Dsp/Dt)= slope on an acceleration graph (rise/run)
Acceleration Graph
+ acceleration (gas pedal)
Constant Speed
(0 acceleration)
(cruise control)
Speed
Acceleration (deceleration)
(brake pedal)
No motion - stopped
Time

8. Acceleration Graphs & Slope & speed
Positive (+) slope = + accel (speeding up) t
speed
Negative (-) slope = - accel (slowing down) t
speed
Zero (0) slope (flat line) = 0 accel (constant speed)

9. Slope & Type of Acceleration
Steeper slopes show greater acceleration
Straight lines = Constant acceleration
Steady increase or decrease in speed
Accelerates quickly
speed t
speed t
decelerates slowly
Accelerates slowly
decelerates quickly
When is the speed = to 0 (stopped)?

10. Discuss This graph
Describe which sport you think this graph represents and why.
Golf
Skydiving
Fishing
100-meter dash
Drag racing
Speed
Time

11. Calculating Acceleration from Slope
Rise–change in the graph on the vertical axis (Speed)
Run–change in the graph on the horizontal axis (Time)
Slope = =
Y2-y1
X2-x1
rise
run
Acceleration=
sp2-sp1
t2-t1
P1 (0 s, 0 km/h)
t1 sp1
P2 (20 s, 20 km/h)
t sp2 P2 a=
sp2-sp1
t2-t1 =
20 km/h - 0 km/h
20 s– 0 s
20 km/h
20 s = P1
= 1 km/h/s

12. Answers to Sample Questions
What is the acceleration of the object from 0 – 20 s?
What is the speed of the object from 20 – 40 s?
What is the speed of the object from 40 – 60 s?
sp2 – sp 1 (rise)
(20–0 m/s)
20 m/s
Acceleration(slope) = = = =
1 m/s/s
t2 – t (run)
( 20 – 0 s)
20 s
sp2 – sp 1 (rise)
(20–20 m/s)
0 m/s
Acceleration(slope) = = = =
0 m/s/s
t2 – t (run)
( 40 – 20 s)
20 s
sp2 – sp 1 (rise)
(0–20 m/s)
-20 m/s
Acceleration(slope) = = = =
-1 m/s/s
t2 – t (run)
( 60 – 40 s)
20 s

13. Acceleration Formula, Units & Power Shape
m/s, cm/min, km/h
Acceleration =
final speed – initial speed
final time – intial time
m/s/s, cm/min/min, km/h/s
s, min, hr
Since:
sp2 = final speed, sp1 = initial speed
t2 = final time, t1 = initial time
a =
(spf – spi)
(tf – ti)
a =
(sp2 – sp1)
(t2 – t1)

14. Acceleration Formula, Units & Power Shape=
final speed – start speed
final time – start time
sp2=final speed, sp1=start speed t2=final time, t1=start time
Since: Then: ÷
Dsp
a =
D sp
D t
Dsp = sp2 – sp1 a Dt
Dt = t2 – t1
 or x

15. Using the Acceleration Power Shape
 or x a Dt
Dsp ÷
A kid is sledding down a hill. When he enters the course his speed is 10 m/s. After 2 seconds he has reached a speed of 26 m/s. What was his acceleration?
Given Formula Setup Solution
List Given Info
And Unknown:
sp1 = 10 m/s
sp2 = 26 m/s
Dt = 2 s
a= ?
Show Needed Equations:
a =
Substitute with Units & Show Math:
a =
Circles Answer with Units:
a =
a = 8 m/s/s
(sp2 – sp1)
26 m/s-10 m/s
16 m/s Dt
2 s
2 s

16. Freefall and gravitational acceleration
Freefall: Objects falling due to gravity
All objects accelerate at the same rate due to gravity during freefall regardless of their mass
Objects may reach terminal velocity sooner due to air resistance
Gravitational acceleration (g) = 9.8 m/s/s on earth

17. Using the Acceleration Power Shape
 or x a Dt
Dsp ÷
A woman jumps from a plane. She opens her parachute five seconds later. How fast was she going when she opened her shoot (disregard air resistance)?
Given Formula Setup Solution
List Given Info
And Unknown:
Dsp = ??
Dt = 5 s
a= g=9.8 m/s/s
Show Needed Equations:
Dsp =
Substitute with Units & Show Math:
Dsp =
Circles Answer with Units:
Dsp = 49.2 m/s a
· Dt
9.8 m/s/s
· 5 s