The difference in the fall speed of a man using a parachute and a stone through air is due to the effects of air resistance or drag. When an object falls through the air, it experiences resistance from the air molecules it encounters, which slows it down.
In the case of a man using a parachute, the parachute provides a large surface area that interacts with the air. As the person falls, the parachute catches a significant amount of air, creating drag. The drag force acts in the opposite direction to the force of gravity, reducing the net downward force on the person. This results in a slower descent speed compared to freefalling without a parachute.
On the other hand, a stone has a relatively small surface area compared to its weight. As it falls through the air, the stone encounters less air resistance, and the drag force acting on it is relatively weak compared to its weight. Therefore, the stone falls through the air more quickly, accelerating under the force of gravity.
In summary, the difference in shape and surface area between a man using a parachute and a stone affects the amount of air resistance or drag they experience. The larger surface area of the parachute slows down the descent of the person, while the smaller surface area of the stone allows it to fall more rapidly.