A constant force of 1.0 N will cause a mass of 1.0 kg to accelerate at a constant rate of 1.0 m/s2 , from which it follows that 1 N = 1 kg * m/s2
If, while in space, we push on a floating weightless ½-kg mass with a constant 1-N force, it will immediately accelerate in the direction of the force, at a rate of 2 m/s2 all the while the force acts.