Okay so if lets start with a law of motion. (Newtons second law of motion)*The rate of change of momentum is proportional to the resultant force and occurs in the directional force*.
This means that f = ma *the attached image shows how to get here *
since f is the force is the one needed to 'obtain' the motion you will notice that if my value of m changes my f chances for example lets take a to be 1 (keep it constant)
lets have m=3 or 120, will change likewise f
a change in f means a change in motion be it deceleration or acceleration
l hope this makes sense and l hope that it's correct
