The speed of a falling object is not directly affected by mass. Air resistance is the deciding factor in the time is takes for an object to reach the ground. Two objects of different mass will accelerate at the same rate. This was discovered by Galileo. Newton's second law states that F=ma. This means that if both accelerate at the same rate, then the force acting on the objects must be different, and the greater the mass, the greater the force of gravity that is acting upon the object.
