1. Relative Motion! (pg. 82 – 83)
Amy, Bill, and Carlos are watching a runner…
According to Amy, the runner’s velocity is vx = 5 m/s
According to Bill, the runner’s velocity is _______ .
According to Carlos, the runner’s velocity is ______.
Who is right?

2. Describing Relative Motion…
Suppose we know that the runner’s velocity relative to Amy is 5 m/s.
How could we represent this / label this?
What about the velocity of Carlos relative to Amy (15 m/s)?
What about flipping perspective?

3. Describing Relative Motion…
What about the velocity of the runner with respect to Carlos?

4. Example 3.9 – pg. 83
Researchers doing satellite tracking of albatrosses in the Southern Ocean observed a bird maintaining sustained flight speeds of 35 m/s – nearly 80 mph! This seems surprisingly fast until you realize that this particular bird was flying with the wind, which was moving at 23 m/s.
What was the bird’s airspeed – its speed relative to the air?

5. Homework Problem: Relative Motion
An airplane pilot wants to fly due west from Spokane to Seattle. Her plane moves through the air at 200 mph, but the wind is blowing 40 mph due north.
What would be velocity of the plane with respect to the ground?
In what direction should she point the plane—that is, in what direction should she fly relative to the air?
Slide 3-36

6. Homework Problem: Relative Motion
An airplane pilot wants to fly due west from Spokane to Seattle. Her plane moves through the air at 200 mph, but the wind is blowing 40 mph due north.
What would be velocity of the plane with respect to the ground?
Slide 3-36

7. An airplane pilot wants to fly due west from Spokane to Seattle
An airplane pilot wants to fly due west from Spokane to Seattle. Her plane moves through the air at 200 mph, but the wind is blowing 40 mph due north.
In what direction should she point the plane—that is, in what direction should she fly relative to the air?

8. Recap – Another example of relative motion
Presume we are swimming in a stream…

9. Recap – cont’d… in reverse!

10. Relative Motion, cont’d.
Consider, swimming ACROSS a river…

11. Relative Motion, cont’d.
Consider, swimming ACROSS a river…
How long does it take to swim across the stream?
How far down stream would you end up?

12. Test Yourself!
A motorboat traveling 4 m/s, East encounters a current traveling 7.0 m/s, North.
What is the resultant velocity of the motorboat?
If the width of the river is 80 meters wide, then how much time does it take the boat to travel shore to shore?
What distance downstream does the boat reach the opposite shore?