Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). So if you want to increase the acceleration, you would have to decrease the mass. So the heavier the objects, the more force you need to move the same distance as lighter objects. Force Equals Mass Times Acceleration F=M*A So.. F=12*5 F=60newtons