2. VELOCITY & ACCELERATION

3. VELOCITY *Describes both the speed & direction of an object

4. VELOCITY Direction *can be expressed using (+) (+) or (-) signs *up, right or forward are considered to be (+)(+) *down, left, or backward are considered to be (-)(-)

5. When can the speed of an object remain constant while the velocity of the object is changing?

6. When the object is changing directions!!!! *the velocity changes because the direction changes.

7. When is the direction of an object always changing? *When the object is turning in a circle.

8. ACCELERATION *Rate of change of VELOCITY

9. ACCELERATION *Occurs when the speed and/or direction of motion changes (  v ) * during a time interval (  t)

10. FORMULA FOR ACCELERATION *a =  v /  t *a = v f - v i / t f - t i

11. 1.) An airplane traveling at a speed of 20 km/min changes to 80 km/min over a distance of 57 km. When the airplane started to speed up it was 1:37 p.m. When the airplane finished its acceleration it was 1:46 p.m. What was the airplane’s acceleration? Sample problem 1

12. Need Information Initial Velocity = 20 km/minInitial Time = 1:37 p.m. Final Velocity = 80 km/minFinal Time = 1:46 p.m. a = v f - v i / t f - t i 80 km/min - 20 km/min 1:46 - 1:37 a = 60 km/min 9 min a = 6.67 km/min 2

13. * speeding up is considered to be + * slowing down is considered to be –

14. Positive and Negative signs indicate both : For ACCELERATION… 1.) Direction of Displacement (Forward/Backward, Left/Right, Up/Down) 2.) Change in Speed (Speeding up, Slowing down)

15. What is the SIGN of acceleration for a car speeding up while moving forward? Speeding up: Positive change in speed Moving forward: Positive direction of displacement Positive x Positive = POSITIVE ACCELERATION Sample Problem 2

16. What is the SIGN of acceleration for a car that is speeding up while moving backwards? Speeding up: Positive change in speed Moving backwards: Negative direction of displacement Positive x Negative = NEGATIVE ACCELERATION Sample Problem 3

17. What is the SIGN of acceleration for a car slowing down while moving backwards? Slowing down: Negative change in speed Moving backwards: Negative direction of displacement Negative x Negative = POSITIVE ACCELERATION Sample Problem 4

18. Negative Acceleration is NOT the same as Deceleration !!!!

19. DECELERATION Refers ONLY to the slowing down of an object The last sample problem demonstrated a positive acceleration sign that included deceleration

20. Acceleration of Coach McKnight on the Interstate S P E D (M/S) T I M E (SEC.) “To calculate total distance covered you must color in the graph.”

21. Acceleration of Coach McKnight on the Interstate T I M E (SEC.) S P E D (M/S) “To calculate total distance covered you must color in the graph.”