Final answer:
The object's displacement cannot be greater than the distance traveled; displacement is the straight-line distance between start and end points with direction, while distance is the total path length without direction. Displacement equals the distance only when traveling in a straight line without changes in direction.
Step-by-step explanation:
The size of an object's displacement cannot be greater than the distance the object travels. Displacement is defined as the shortest straight-line distance from the starting point to the ending point of an object's path and includes direction, making it a vector quantity. On the other hand, the distance traveled is the total length of the path taken and does not involve direction, making it a scalar quantity. In the only case where the magnitude of displacement equals the distance traveled is when the object travels in a straight line without changing direction.
For example, if a person walks in a rectangle starting and ending at the same corner, their displacement is zero as they end up at the starting point, but the distance traveled is the perimeter of the rectangle. The magnitude of displacement (which is just the size of the displacement without direction) and displacement are exactly the same when the path does not curve or loop back on itself, as no direction change is involved.
When bacteria move using flagella, they often travel in a zigzag or back-and-forth path. As a result, even though the total distance traveled is large, their displacement is small since they do not end up far from where they started. Their movement demonstrates the difference between distance and displacement.