In fact, momentum is only generated by omitting unnecessary steps in the process of Newton's law of motion. How does the change of impulse = momentum of combined external force derive the expression of ft=m△v? F/m=a=△v/t, you will find that by using the momentum theorem, we can calculate F, T, M and △v without calculating acceleration. Because it is obviously meaningless to calculate A, we artificially define such a quantity, which is called momentum and expression mv. The definition of impulse is the same. People found that ft=m△v, so they defined ft as impulse.

It should be noted that physics is a practical subject, such as acceleration, which is actually artificially defined. At that time, because we need it in the calculation; Another example is the electric field, which is also a defined state of matter. Who can strictly prove its existence? The main reason is that this theory can explain imagination, so it is right.

It has always been proved by physics that this mathematics is completely different. For example, Newton's laws of motion have been proved to be wrong, at least imperfect, but we still use them. Why? Because the calculation errors of relativistic mechanics and Newtonian mechanics can be ignored for macroscopic low-speed objects.

Off topic, back to the topic, to understand momentum and impulse, you just need to think of them as a quantity in the calculation process.