Otherwise, newton's first law of motion says that an object will continue to stay at rest or at a until a force is applied to it. *uniform speed in a straight line

The answer is: uniform speed in a straight line.

Jusitification.

That is Newton's first law or Law of Inertia.

Galileo already expressed the same idea. Before that, during almost 2000 years it prevailed the Aristotelian idea that the objects move when there is a force acting.

The Inertia law states that the objects may remain in permanent uniform straight motion if none force acts on them.

The Arestotelian idea was based in the ordinary observation that when you do not push an object it slows down until stoping.

But, the reason after this behavior is that the objects slow down until stoping due to a force: friction force for example.

It may possibly be c i think |-/