1. KINEMATICS: LESSON 2

2. AVERAGE SPEED VS. AVERAGE VELOCITY
Example: At a track meet at Redwater School, a runner does one complete 800 metre lap in 1.5 minutes. Assuming she starts and stops at the same point: a. What was her average speed during this lap? b. What was her average velocity for this lap? First let's convert minutes to seconds:
1.5 min * (60 sec ) = 90 seconds
1 min
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3. AVERAGE SPEED VS. AVERAGE VELOCITY
The total distance covered was 800 metres. The total time was 90 seconds.
         The average speed = 800 m = 8.9 m/s.
90s
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4. AVERAGE SPEED VS. AVERAGE VELOCITY
Example:
   b. What was her average velocity for this lap?
b.   The total displacement was zero. She returned to the starting point! The total time was 90 seconds.
         The average velocity = m = 0 m/s
90 s
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5. POSITION-TIME GRAPHS & UNIFORM MOTION
What is the golf ball’s displacement after each second?
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6. TABLE AND GRAPH OF GOLF PUTT
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7. DISCUSSION OF GOLF PUTT: TABLE AND GRAPH
Notice that the graph is a straight line.
A straight line has a constant slope.
What does constant slope tell you about the ball’s motion?
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8. CALCULATING SLOPE OF THE GRAPH
The equation for slope :
A change in position is displacement.
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9. DISCUSSION OF SLOPE OF THE GRAPH
Notice that the units of the slope are m/s. These units indicate speed or velocity.
The slope of a position-time graph gives us velocity.
change in position per unit time.
called average velocity
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10. DOES DIRECTION AFFECT VELOCITY?
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11. UNIFORM MOTION
If an object moves at constant velocity (constant magnitude and direction), the object is undergoing :
uniform motion.
A position-time graph for an object at rest is:
a horizontal line.
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12. CHANGING THE FRAME OF REFERENCE
If we were to designate the hole as the origin (rather than start point of ball), your data table would start at 5.0 m at time 0.0 s.
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13. TABLE AND GRAPH OF GOLF PUTT: NEW FRAME OF REFERENCE
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14. CALCULATING SLOPE OF THE GRAPH: NEW FRAME OF REFERENCE
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15. SUMMARY: The slope of a position-time graph represents velocity.
The velocity is the average velocity for the time interval.
Your choice of reference frame affects the direction (sign) of your answer.
A straight line on a position-time graph represents uniform motion.
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16. EXAMPLE
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17. EXAMPLE
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18. EXAMPLE
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19. EXAMPLE
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20. EXAMPLE 1.4
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21. HOMEWORK:
Text: Read Page 11 – 20
Workbook:
Physics 20