Even if there is no resistance to the objects' motion in air, the two objects will still experience different rates of acceleration due to gravity. The hammer will accelerate towards the ground faster than the feather due to its greater mass.
This is because the gravitational force acting on an object is directly proportional to its mass. The hammer has more mass than the feather, so it will experience a greater gravitational force pulling it towards the ground. As a result, the hammer will accelerate towards the ground faster than the feather, even in the absence of air resistance.
Additionally, the acceleration due to gravity is the same for all objects near the surface of the Earth, regardless of their mass. This means that both the hammer and the feather will experience the same acceleration due to gravity, but because the hammer has more mass, it will require more force to overcome its inertia and accelerate it towards the ground.