1. Describing Motion Acceleration
Motion & Forces
Describing Motion
Acceleration

2. Speed & Velocity v d t
Speed .

3. Speed & Velocity
Instantaneous Speed .
Average Speed

4. Speed & Velocity
Velocity .

5. Acceleration a
vf - vi t
Acceleration .
a: .
vf: .
vi: .
t: .

6. Acceleration, Speed and Velocity
When you think of acceleration, you probably think of something speeding up. However, …… .

7. Acceleration
If the acceleration is in the same direction as the velocity, the speed increases and the acceleration is .

8. Acceleration
If the speed decreases, the acceleration is in the opposite direction from the velocity, and the acceleration is .

9. Changing Direction
A change in velocity can be either a change in how fast something is moving or .
Any time a moving object changes direction, its _________ changes and it is _____________

10. Changing Direction
The speed of the horses in this carousel is constant, but the horses are accelerating because their direction is _______________

11. Acceleration
Positive acceleration .
Negative acceleration .

12. t a Calculations t = 3 s vf = 32 m/s a = ? vi = 10 m/s GIVEN: WORK:
A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration?
GIVEN:
vi = 10 m/s
t = 3 s
vf = 32 m/s
a = ?
WORK:
a = (vf - vi) ÷ t
a = (32m/s - 10m/s) ÷ (3s)
a = 22 m/s ÷ 3 s
a = 7.3 m/s2 a
vf - vi t

13. t a Calculations t = 12 s vf = 6.7 m/s a = ? vi = 0 m/s GIVEN: WORK:
  A skater goes from a standstill to a speed of 6.7 m/s in 12 seconds.  What is the acceleration of the skater?
GIVEN:
vi = 0 m/s
t = 12 s
vf = 6.7 m/s
a = ?
WORK:
a = (vf - vi) ÷ t
a = (6.7m/s - 0m/s) ÷ (12s)
a = 6.7 m/s ÷ 12 s
a = .56 m/s2 a
vf - vi t

14. t a Calculations a = (vf - vi) ÷ t t = 5 s a = (0m/s - 9m/s) ÷ (5s)
As a shuttle bus comes to a normal stop, it slows from 9.00m/s to 0.00m/s in 5.00s.  Find the average acceleration of the bus.
     
GIVEN:
vi = 9 m/s
t = 5 s
vf = 0 m/s
a = ?
WORK:
a = (vf - vi) ÷ t
a = (0m/s - 9m/s) ÷ (5s)
a = -9 m/s ÷ 5 s
a = -1.8 m/s2 a
vf - vi t

15. Calculations
How long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s2?
GIVEN:
t = ?
vi = 30 m/s
vf = 0 m/s
a = -3 m/s2
WORK:
t = (vf - vi) ÷ a
t = (0m/s-30m/s)÷(-3m/s2)
t = -30 m/s ÷ -3m/s2
t = 10 s a
vf -vi t

16. Amusement Park Acceleration
Engineers use the laws of physics to design amusement park rides that are thrilling, but harmless.
The highest speeds and accelerations usually are produced on steel roller coasters WHY??

17. Amusement Park Acceleration.

18. Amusement Park Acceleration
When riders go around a sharp turn, they also are accelerated.
This acceleration makes them feel as if a force is pushing them toward the side of the car.
WEEEEEEEEEEE --- Mr. Powell Loves Roller Coasters EVERYONE !!!!