Final answer:
Patrick's average velocity for the trip is 0.278 m/s south, determined by dividing the total displacement of 50.0 m south by the total time of 180.0 seconds.
Step-by-step explanation:
To determine Patrick's average velocity for the entire trip, we need to consider the total displacement divided by the total time taken. His total displacement is the net distance covered in a particular direction. Therefore, the total displacement is 70.0 m south - 20.0 m north = 50.0 m south. The total time taken for the trip is 150.0 seconds + 30.0 seconds = 180.0 seconds.
The average velocity can be calculated by the formula:
Average velocity = Total displacement / Total time
In this case:
Average velocity = 50.0 m south / 180.0 seconds = 0.278 m/s south
Hence, the correct answer is a velocity of 0.278 m/s south.