Final answer:
Sally's average velocity for her entire trip is approximately 10.26 m/s west. This is calculated by summing her displacements during each segment of her trip and dividing by the total time.
Step-by-step explanation:
To calculate Sally's average velocity for her entire trip traveling west, we must first determine her total displacement and the total time taken. Since she's traveling in the same direction (west) for the entire trip, we can simply add her displacements for each segment of her trip and divide by the total time.
The first segment of her trip:
Velocity = 12 m/s
Time = 13 minutes = 13 x 60 seconds = 780 seconds
Displacement = Velocity x Time = 12 m/s x 780 s = 9360 m
The second segment of her trip:
Velocity = 9 m/s
Time = 18 minutes = 18 x 60 seconds = 1080 seconds
Displacement = Velocity x Time = 9 m/s x 1080 s = 9720 m
Total displacement = 9360 m + 9720 m = 19080 m
Total time = 13 minutes + 18 minutes = 31 minutes = 31 x 60 seconds = 1860 seconds
Now, to find her average velocity, we divide her total displacement by the total time:
Average velocity = Total displacement / Total time
Average velocity = 19080 m / 1860 s ≈ 10.26 m/s west.