Question

A clod of dirt falls from the bed of a moving truck. (a) What is the direction of its velocity relative to the truck just before it hits? (b) Is this the same as the direction of its velocity relative to the ground just before it hits? Explain your answers.

a) Upward, Upward
b) Downward, Downward
c) Downward, Upward
d) Upward, Downward

Answer 1

Relative to the truck, the velocity of the clod of dirt is downward just before it hits the ground. Relative to the ground, the dirt has both a forward and downward velocity, combining its initial horizontal motion and its vertical acceleration due to gravity.

Step-by-step explanation:

The question involves understanding the relative velocity of a clod of dirt as it falls from a moving truck. When considering the motion relative to the truck, right before the clod of dirt hits the ground, it has a velocity directed downward because it is falling under the influence of gravity. This is assuming that the dirt has not reached the ground yet and is still in free fall.

However, because the truck is moving forward, relative to the ground, the clod also carries forward motion it had while it was still in the truck. Thus, relative to the ground, the clod has a forward and downward velocity, the result of its horizontal motion from the truck and its vertical motion due to gravity.