In the absence of any external factors such as air resistance, both the large stone of 20 kg and the small stone of 5 kg will reach the ground simultaneously. This is because in a vacuum or in the absence of air resistance, all objects fall with the same acceleration due to gravity, regardless of their mass.
According to the principles of free fall, in the absence of air resistance, all objects near the surface of the Earth experience the same acceleration due to gravity, which is approximately 9.8 meters per second squared (9.8 m/s^2). This means that regardless of their mass, objects will accelerate at the same rate towards the ground.
Therefore, in this scenario, both the large stone and the small stone will experience the same acceleration due to gravity, and they will fall with the same rate of acceleration. Consequently, they will reach the ground at the same time.