1. Acceleration

2. Bell Ringer: 9/21
What would the velocity graph look like?

3. 2. What are the three devices on a car that can make it change its velocity?

4. They change the rate of speed over time
What pedal is this?
What pedal is this?
They change the rate of speed over time

5. What device in your car cause it to change DIRECTION?

6. Bell work
What is it’s acceleration?

7. Acceleration
The rate (time) at which an object changes its velocity

8. Acceleration is ANY change in velocity.
When you are in a car and you step on the “accelerator” the car accelerates (speeds up)
POSITIVE acceleration
When the brakes are applied, the car also accelerates (slows down)
Negative acceleration (deceleration)

9. VELOCITY Speed Displacement
Recall that velocity is speed AND direction
VELOCITY
Speed Displacement
So…. If a car goes around the block at a constant speed of 30 mph, is it accelerating???

10. Distance & Displacement
What is displacement?
Change in POSITION
From the initial position to final position.
Where did it “end up” compared to where it started?

11. Galileo rolled balls down a series of ramps.
As the ramps got higher, the balls rolled at a greater speed.
Their speed increased.
Galileo said that they were…..
Accelerating.

12. Acceleration Units: m/s2
Acceleration occurs when an object
Speeds up (+)
Slows down (-)
Change in direction
Units: m/s2
Acceleration= Final velocity – initial velocity
Time
Accel = Δv t

13. Acceleration formula a = ∆v t a = velocityfinal – velocityinitial time
∆ “change in”

14. Positive & Negative Acceleration
Positive acceleration
“speeding up”
Negative acceleration
“slowing down”

15. Practice Problem #1
If a car starts from rest, and reaches a speed of 100 m/s north in 10 seconds, what is the acceleration? G U E S
acceleration
Final V – Initial V
time
Initial velocity =
rest 0 m/s
Final velocity =
100 m/s
Time = 10 sec
+10 m/s/s
100 m/s – 0 m/s
10 sec or
+10 m/s2

16. Practice Problem #2
What is the acceleration when a car slows down from 100 km/hr to 60 km/hr in 5 seconds? G U E S

17. Practice Problem #3
What is the acceleration of a dragster that reaches a speed of 200 miles/hr in 4 seconds? G U E S

18. Work Sheet
Work on the Acceleration worksheet with your shoulder partner

19. Practice Problem
Describe the motion of the object at each part on the graphs.
Time
Velocity D E F
Distance
Time A B C

20. Bell Ringer
Which of the following are the units for acceleration? (hint: more than one answer)
a) m/s2 b) km/hr s
c) m/s d) miles
Which of the following is not accelerating?
A car slowing to a stop at a stop sign
You riding a Ferris Wheel
The moon orbiting the Earth
A cyclist riding constantly at 2 m/s on a straight path

21. Bell Ringer
Which of the following are the units for acceleration? (hint: more than one answer)
a) m/s2 b) km/hr/s
c) m/s d) miles
Which of the following is not accelerating?
A car slowing to a stop at a stop sign
You riding a Ferris Wheel
The moon orbiting the Earth
A cyclist riding constantly at 2 m/s on a straight path