The duration of a fall does influence the impact force of an object hitting the ground, as the speed of the falling object increases with time when neglecting air resistance. The impact force is determined by how quickly the object decelerates upon hitting the ground. Assuming a constant stopping time, the force can be calculated using F=ma, where acceleration is derived from speed and stopping time. Therefore, a longer fall duration results in a higher impact force, given the same stopping conditions. This relationship holds true for objects falling near Earth's surface.