Both objects are in a state of free fall; hence, a marble and a feather reach the ground together when they are dropped simultaneously in a vacuum from the same height.

Explanation

In a vacuum, the upthrust due to air is absent. As a result, the only notable downward pulling force that acts on each falling object is the force due to gravity. Although this force varies for different objects with different masses. The acceleration of each object remains the same and is equal to the acceleration due to gravity (g). $\rm g = \frac{GM}{r^{2}}$, where G is the Gravitational Constant, M is the mass of the planet, and r is the distance between the centers of the body and the planet.

When we drop the bodies, they have no initial velocity (u = 0). Hence, their displacement covered is given by the following equation of motion $\rm s = \frac{1}{2} g t^{2}$.

If they cover the same displacement, s = h, then,

$$\rm t^{2} = \frac{2h}{g}$$

Here, h and g are the same for any two objects falling in the vacuum. Hence, they travel the required displacement in equal time.