In the absence of any other forces (such as air resistance), if you drop two objects of different masses but the same size from the same height, they will hit the ground at the same time. This observation is known as the principle of equivalence or the principle of free fall.
According to Newton's second law of motion, the force acting on an object is equal to its mass multiplied by its acceleration (F = m * a). When an object is in free fall near the surface of the Earth, it experiences the acceleration due to gravity, which is the same for all objects regardless of their mass. This acceleration is approximately 9.8 m/s².
Since the acceleration due to gravity is the same for both objects, their masses cancel out in the equation F = m * a. Therefore, both objects experience the same force, and as a result, they accelerate at the same rate. As a result, they will hit the ground simultaneously.
It's worth noting that this explanation assumes idealized conditions without considering air resistance, which can have an effect on the motion of objects in real-life scenarios. In the presence of significant air resistance, the objects with different masses and surface areas may experience different resistive forces, leading to different falling times.