I am a little confused about forces when time is considered. I understand the nature of forces, ie that they are a push or a pull and that they induce a change in momentum and thus an acceleration. However, my question is, how could we solve such a problem as "If a force of 2 N is applied to a 4 kg block for 6 seconds, what is the resulting acceleration?" When solving force problems, we usually always refer to Newton's second law, F = ma, but I do not see how this equation helps solving problems that involve the application of force over a time interval. As a side note, if given a problem such as "If a force of 4 N is applied to a 2 kg box, what is the resulting acceleration?" Is 2 m/s^2 really the correct answer? What if we apply the 4 N for 0.5 s rather than 0.1 s? How does F = ma take this into account?