# Isaac Newton and Definition of Force

Isaac Newton in Principia Law II says:

"the change of motion is proportional to the motive force impressed, and takes place following the straight line in which that force is impressed". "If some force should generate any motion you please, a double will generate a double....whether it has been impressed all at once, or gradually and successively".

The textbooks often say that "the modern formulation is $F=ma$". But change of motion is $\Delta (mv)$, and the force impressed is over time. Would it be fair to say that what Newton is stating is the modern equation of Impulse, not Force?