What is newton's first law of motion?

A body continues in uniform motion unless acted on by an external force.

"Uniform motion" is another way of saying that the object has
no acceleration.  THAT means that its speed and direction aren't
changing.  It's moving in a straight line, and at a constant speed
(which may be zero). 

If you want to change the object's speed OR direction, then you'll
need to apply some force to it.  There's no other way.