Suppose that a similar force is applied to each of the objects, that is: F=m_1a_1, F=m_2a_2. We know the masses, so F=1a_1 F=2a_2. F=a_1, 1/2F=a_2. In other words, with the same force applied to each object, the one with the 1kg mass will have twice the acceleration of the 2kg mass