Recalling the definition of acceleration as change in velocity/time interval, we led into the idea that force causes acceleration. Unbalanced forces acting on an object cause the object to accelerate. Acceleration is directly proportional to the net force acting on it. Demonstrating the effects of increase mass on acceleration, we conclude that for a constant force, an increase in the mass will result in a decrease in acceleration. Acceleration is inversely proportional to mass. Newton's second law states that the acceleration produced by a net force on an object is directly proportional to the magnitude of the in the same direction, and inversely proportional to the mass of the object.