Final answer:
The correct answer is option b, which states that a swimmer's average velocity can be zero if their total displacement is zero, even after swimming several laps.
Step-by-step explanation:
The correct answer is option b. His average velocity is zero because his total displacement is zero. Velocity is a vector quantity, which means it has both magnitude and direction. When a swimmer completes multiple laps in a pool, they end up at the starting point after swimming an equal distance in opposite directions.
Since displacement is the shortest distance between the starting and ending points, and the direction from start to finish, if a swimmer finishes at the starting point, the displacement is zero.
Thus, even though the swimmer has swum a certain distance, if they finish where they started, their average displacement over time, and consequently their average velocity, is zero.
The correct answer is option b. His average velocity is zero because his total displacement is zero.
Since swimming one lap is defined as going across a pool and back again, swimming 3 laps means the swimmer has gone across the pool and back 3 times. If the swimmer returns to the starting point after swimming 3 laps, their total displacement is zero.
Displacement is a vector quantity that represents the straight-line distance and direction from the starting point to the ending point. In this case, since the swimmer returns to the starting point, their displacement is zero and therefore their average velocity is also zero.