Final answer:
Bill's average velocity for his 1-minute round trip to Andy's house and back is zero because his starting and ending points are the same, resulting in no displacement.
Step-by-step explanation:
To calculate Bill's average velocity for his round trip to Andy's house, you need to understand the difference between velocity and speed. Velocity is a vector quantity, meaning it has both magnitude and direction, whereas speed is scalar and only has magnitude. When Bill runs 400 meters to Andy's house and then 400 meters back home, his displacement is zero because he ends up at the starting point. The total time taken for the trip is 1 minute (or 60 seconds).
The formula for average velocity is displacement divided by time. Since the displacement is zero (he starts and ends at the same location), the average velocity for the entire trip is also zero, regardless of the time taken or the distance traveled. In contrast, if we were calculating his average speed, we would divide the total distance traveled (800 meters) by the total time (60 seconds), resulting in an average speed of 13.33 meters per second.