A heavier disc will have less air resistance than a lighter disc however due to the force required to accelerate the disc being directly proportional to the mass of the disc this will decrease the acceleration of the disc , assuming that the force of projection is constant .
A heavier disc has less air resistance than a lighter disc , because the force required to accelerate the disc is directly proportional to the mass of the disc . 
 This decreases the acceleration of the disc , assuming that the force of projection is constant .