1. Agenda for 4/20/15 Acceleration Notes
HW - Acceleration Calculations
Quiz next week

2. Unit 7 - Motion
Acceleration

3. Acceleration is the rate of change of velocity
Acceleration is the rate of change of velocity. When the velocity of an object changes, the object is accelerating.
A change in velocity can be either a change in how fast something is moving, or a change in the direction it is moving.
Acceleration occurs when an object changes its speed, its direction, or both.

4. Speeding Up and Slowing Down
If the acceleration is in the same direction as the velocity,
the speed increases and the acceleration is positive.

5. Speeding Up and Slowing Down
Acceleration
Speeding Up and Slowing Down
If the speed decreases, the acceleration is in the opposite
direction from the velocity, and the acceleration is negative. (aka decelerating).

6. Units for acceleration = m/s2 Round to the nearest tenth.
Calculating Acceleration:
Change in Velocity = final velocity – initial velocity
= vf – vi
Acceleration (meters/seconds2) =
Units for acceleration = m/s2
Round to the nearest tenth.

7. Examples:
Suppose a jet airliner starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s.
Because it started from rest, its initial speed was zero.
A = final velocity – initial velocity
time
A = 80 m/s – 0 m/s
20 s
4 m/s2

8. Now imagine that a skateboarder is moving in a straight line at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is the skateboarder’s acceleration. Is it positive or negative?
The final speed is zero and the initial speed was 3 m/s.
A = final velocity – initial velocity
time
A = 0 – 3 m/s
2 s
A = -1.5 m/s2

9. A ball is dropped from a cliff and has an acceleration of 9. 8 m/s2
A ball is dropped from a cliff and has an acceleration of 9.8 m/s2. How long will it take the ball to reach a speed of 24.5 m/s?
A = final velocity – initial velocity
time
9.8 = 24.5 – 0 x
2.5 seconds

10. Amusement Park Acceleration
Engineers use the laws of physics to design amusement park rides.
The highest speeds and accelerations usually are produced on steel roller coasters.

11. Agenda for 4/10/14 Motion Study Guide Whiteboard review Quiz tomorrow
Just in case
you’ve been
Wondering 

12. Question 1 Acceleration is the rate of change of __________.
Section Check
Question 1
Acceleration is the rate of change of __________.

13. Section Check
Answer
The correct answer is velocity. Acceleration occurs when an object changes its speed, direction, or both.

14. Question 2 Which is NOT a form of acceleration?
Section Check
Question 2
Which is NOT a form of acceleration?
A. maintaining a constant speed and direction
B. speeding up
C. slowing down
D. turning

15. Section Check
Answer
The answer is A. Any change of speed or direction results in acceleration.

16. Section Check
Question 3
What is the acceleration of a hockey player who is skating at 10 m/s and comes to a complete stop in 2 s?
A. 5 m/s2
B. -5 m/s2
C. 20 m/s2
D m/s2

17. Section Check
Answer
The answer is B. Calculate acceleration by subtracting initial velocity (10 m/s) from final velocity (0), then dividing by the time interval (2s).
(0 m/s – 10 m/s) = – 5 m/s 2s

18. Agenda for 4/19/13 Go over homework Make accelerometer
Test accelerometer
HW – Speed vs Time worksheet ( Do the 2 questions on acceleration)

19. Accelerometers
Materials: index cards, paper protractors, string, washer, tape
1) Write G-Force #’s on paper protractor
2) Cut out paper protractor
3) Glue to index card
4) Tie string on washer
5) Tape string to index card
6) Tape index card to ruler