1. Speed, Velocity, and Acceleration SPH3U UNIT 1: KINEMATICS

2. Warm-up: Challenge Question!  A robotic toy airplane is flies 32 meters [N 40° W] and then turns and flies 15 meters [N 12° E]. What is the total displacement?

3. Recall  In Physics, we measure things in vector quantities and scalar quantities. Vectors have a magnitude and a direction.  Distance is a scalar quantity.  Displacement is a vector quantity.

4. Speed and Velocity  In English, the words ‘speed’ and ‘velocity’ are often used interchangeably to mean the same thing.  In Physics, these words have two different meanings, because ‘speed’ is actually a scalar quantity and ‘velocity’ is actually a vector quantity.

5. Speed and Velocity SpeedVelocity Scalar quantityVector quantity Example: 3 m/sExample: 3 m/s [North] Speed = v

6. Speed and Velocity SpeedVelocity

7. Uniform Motion  Uniform motion is what we have when velocity is constant. Answer True / False: An object moving at 3m/s straight across the room has uniform motion An object moving at 3m/s in a circle has uniform motion An object moving straight across the room but slowing down has uniform motion

8. Uniform Motion  Uniform motion is what we have when velocity is constant. Answer True / False: T An object moving at 3m/s straight across the room has uniform motion F An object moving at 3m/s in a circle has uniform motion F An object moving straight across the room but slowing down has uniform motion

9. Uniform Motion  Any change in speed or direction results in non-uniform motion.  Most motion is non-uniform  Non-Uniform motion = accelerated motion  Instantaneous velocity or instantaneous acceleration are the exact values of each in that instant. For uniformly accelerated motion, the instantaneous acceleration equals the average acceleration at any point.

10. Acceleration

12.  Negative Acceleration:  An object that is slowing down could be said to be decelerating 2 m/s 2 [North] or acceleration -2m/s 2 [South]. These are equivalent.

13. Acceleration due to Gravity  Question: Do all objects fall to the earth at the same rate? Your response: Yes / No

14. Demonstration  If we drop a textbook and a piece of paper at the same time, from the same height, will they fall at the same rate or different rates?  Your response: …..  Why you think so: ….

15. Demonstration  If we change things slightly….  What did we observe......  Conclusion:

16. Demonstration  If we change things slightly….  What did we observe......  Conclusion: Things fall to the earth at the same rate (with no air resistance). (This is because gravity affects all things the same way).

17. Example 1 A dog is walking down the street. He walks 30m [North] and then 40 m [West]. If it takes him 40 seconds to complete this trip, what is his average speed? What is his average velocity?

18. Example 2 When a ball is thrown upward, it experiences a downward acceleration of 9.8m/s 2 [down] (neglecting air resistance). With what velocity must a ball leave the person’s hand in order to go up 2.2 seconds before reaching its maximum height and stopping?

19. Homework  Complete the following questions:  Pg. 20 # 1-3, 5 - 8  Pg. 24 # 1 - 3