We're missing one essential piece of information that we need in order to answer this question. You have not specified <em>what planet</em> the object is falling on. The answer depends on the gravitational acceleration on that planet, and they're all different.
Without that information, we'll just go ahead and assume that the object is falling to the surface of the Earth. Wherever on Earth this tense drama is unfolding, the acceleration of gravity is going to be around <em>9.8 m/s²</em> everywhere.
So THAT's the object's acceleration if there is no air resistance. The object's MASS makes no difference. It doesn't matter whether the object is a sparrow feather or a school bus. Heavier objects DO NOT fall faster than light objects.
If there is no air resistance, then ALL objects fall with the same acceleration. It's called the "acceleration of gravity" on that planet or moon, and you can easily look it up. It's 9.8 m/s² on Earth, 1.62 m/s² on the Moon, 3.71 m/s² on Mars, 8.87 m/s² on Venus, and 24.8 m/s² on Jupiter.
