Can we say that momentum is the reason behind inertia? like momentum explains inertia. Momentum:- mass * velocity net force is the rate of change of momentum. f=mv/t and Inertia:- it is the tendency of an object to stay in the state of motion it currently is in i.e resist the change of state of motion. For example:- a car speeds up (accelerates) but later at some point the velocity becomes constant(assume there is no other force acting on the object).now the net force on the object is zero(so is acceleration) but the object continues to move with constant velocity and hence it has the same momentum (since mass isn't changing and neither is velocity). so no force but momentum is still there. momentum is the energy which the moving object has right? when there is some velocity the momentum remains constant and the object keeps moving because of this and when the velocity is zero then momentum is zero and thus the object remains at rest. here not changing its velocity is the the objects 'tendency' we call it inertia and momentum is what keeps the object moving. so what i think is: inertia tells us that the state of motion will not change and momentum tells us the reason behind it(it is the reason) sort of like "it happens" and "why it happens" am i right right? or i am confusing them both?