1. 3.1 Notes, Part B

2. Today’s Objectives Calculate the average speed of an object.
Explain the difference between speed and velocity.

3. Speed Speed = = Distance an object travels per unit of time Distance
Distance in meters
Time in second
Scalar quantity
refers to "how fast an object is moving.“
Distance
Speed =
time d = t

4. Speed changing

5. Speed
SI unit for speed is
m/s

6. Average speed = total distance traveled divided by total travel time
Km/hour
Instantaneous speed = speed at a single instant of time
Speedometer measures this

7. Example
While on vacation, Lisa traveled a total distance of 440 miles. Her trip took 8 hours. What was her average speed?
To compute her average speed, we simply divide the distance of travel by the time of travel.

8. Velocity Speed and direction Vector quantity
refers to "the rate at which an object changes its position.“
I traveled south at 60 mi/h to get to school
Velocity changes if…
You change speed
You change direction

9. Average velocity
Different from average speed

10. Example 1 Average speed = 0.50 m/s Average velocity = 0 m/s
Physics Teacher again, walked 12 m in 24 seconds
Displacement = 0 m
Average speed = 0.50 m/s
Average velocity = 0 m/s

11. Example 2 Average speed = 140 m/min Avg. velocity = 46.7 m/min, right
Cross-country skier again
Distance = 420 m
Displacement = 140 m, right
Average speed = 140 m/min
Avg. velocity = 46.7 m/min, right

12. Example 3 Average speed = 9.5 yds/min
Football coach again,
Distance = 95 yds
Displacement = 55 yds, left
Average speed = 9.5 yds/min
Avg. velocity = 5.5 yds /min, left

13. In-class Assignment/Homework
Finish 3.1 B Lecture Tutorial