What is Newton's Second Law of Motion?

Newton's Second Law of Motion According to this law, the rate of change of momentum is directly proportional to the applied force. The change in momentum takes place in the direction of applied force. Newton's II law gives the quantitative definition of force. i.e. $\quad \vec{F}=\frac{\Delta \vec{p}}{\Delta t}$ If $\Delta t$ is vanishingly small then $\vec{F}=\frac{\overrightarrow{d p}}{d t}$ Out of Newton's three laws of motion, the most fundamental one is the second law, because I and III law...