Answer:
Increasing mass decreases acceleration because of inertia. the heavier something is the more inertia it has. It's harder to change the direction of a train than a car since the train has more weight. It's easier to push an empty cart than one full of food. The gravitational pull and the mass of the object push harder on the ground which needs more energy to push therefore it accelerates slowly. Like push a basketball it will go further than a bowling ball
Also, Newton's second law force equals mass times acceleration. if force increases and acceleration, then mass decreases.
