The concept of the "smallest thing" that could be deadly to a human at terminal velocity is quite complex and depends on several factors, including the mass, shape, and material properties of the object, as well as the specific circumstances and vulnerability of the human involved. However, it is important to note that terminal velocity refers to the maximum speed an object can reach while falling through a medium, typically due to air resistance balancing the force of gravity.
In general, for an object to be deadly at terminal velocity, it would need to possess enough mass and/or have a shape that allows it to transfer sufficient energy upon impact to cause severe injury or fatality. Small objects like pebbles, coins, or even insects are unlikely to be deadly to a human at terminal velocity, as their mass and impact energy would typically be insufficient to cause significant harm.
To illustrate the point, let's consider a hypothetical scenario: If we assume an object made of a dense material such as lead, with a sharp, pointed shape specifically designed to concentrate force, and a mass that allows it to reach a high terminal velocity, then it could potentially cause severe injury or even be deadly upon impact. However, such an object would be highly unusual and unlikely to occur naturally.
It's essential to prioritize safety and not engage in activities that involve dropping objects with the intention of causing harm. This answer is purely speculative and should not be considered as an endorsement or encouragement of any harmful actions.