The two balls land at the same time due to the principle of gravity. Both balls are subject to the same gravitational force, which pulls them towards the Earth at the same rate, regardless of their mass or initial conditions. This is described by Newton's law of universal gravitation, which states that the force of gravity is directly proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them.

The acceleration due to gravity on Earth is approximately 9.8 meters per second squared (m/s²). This means that any object, regardless of its mass, will fall at the same rate in a vacuum. When the two balls are dropped from the same height and released simultaneously, they will both experience the same acceleration due to gravity, causing them to hit the ground at the same time.

For example, if two balls are dropped from a height of 10 meters, they will both hit the ground after approximately 1.43 seconds (calculated using the formula t = √(2h/g), where h is the height and g is the acceleration due to gravity). This is because the time it takes for an object to fall is independent of its mass, as long as air resistance is negligible.

In real-world scenarios, air resistance can affect the time it takes for an object to fall. However, for small objects like balls, air resistance is generally not significant enough to cause a noticeable difference in the time it takes for them to hit the ground. Therefore, the two balls will land at the same time, assuming they are dropped from the same height and released simultaneously.