Final answer:
The direction of the clod of dirt's velocity relative to the moving truck just before it hits the ground is vertically downward, while relative to the ground, it has both horizontal and vertical components making it diagonal.
Step-by-step explanation:
When a clod of dirt falls from the bed of a moving truck and strikes the ground directly below the end of the truck, the direction of its velocity relative to the truck just before it hits is vertically downward
This is because as the clod of dirt falls, it retains the horizontal velocity it had due to the motion of the truck. However, relative to the ground, the velocity of the clod of dirt has two components just before it hits: a horizontal component (due to the motion of the truck) and a vertical component (due to gravity). Thus, the velocity relative to the ground is diagonal, not just vertical. Since the clod lands directly below the end of the truck, this means that the truck's horizontal velocity matches the horizontal component of the clod's velocity as it falls. Despite this match in horizontal velocities, they are not the same because the velocity relative to the ground also has the added vertical component due to gravity.