1st Law of MotionInertiaMotion doesn't change without an outside force..
Chapter 14 - Force & Motion
Newton's Laws of Motion
 2nd Law of MotionF = maThis explains how much a force will change the motion of an ojbect.
 3rd Law of MotionFor every action...the force will effect the motion of both of the objects
1st Law             Inertia
 Newton's first law of motion states that"An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force."Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.
 Newton's conception of inertia stood in direct opposition to more popular conceptions about motion.The thought prior to Newton's day was that it was the natural tendency of objects to come to rest.Moving objects, so it was believed, would eventually stop moving; a force was necessary to keep an object moving. But if left to itself, a moving object would eventually come to rest and an object at rest would stay at rest; thus, the idea which dominated people's thinking for nearly 2000 years prior to Newton was that it was the natural tendency of all objects to assume a rest position.
 Galileo & Inertia
Galileo developed the concept of inertia. Galileo reasoned that
moving objects eventually stop because of a force called friction.
In experiments using a pair of inclined planes facing each other,
Galileo observed that a ball will roll down one plane and up the
opposite plane to approximately the same height. If smoother
planes were used, the ball would roll up the opposite plane even
closer to the original height. Galileo reasoned that any difference
between initial and final heights was due to the presence of
friction. Galileo postulated that if friction could be entirely
eliminated, then the ball would reach exactly the same height.

Galileo further observed that regardless of the angle at which
the planes were oriented, the final height was almost always
equal to the initial height. If the slope of the opposite incline was
reduced, then the ball would roll a further distance in order to
reach that original height.
 Newton's first law of motion declares that a force is not  needed to keep an object in motion. Slide a book across a table and watch it slide to a rest position. The book in motion on the table top does not come to a rest position because of the absence of a force; rather it is the presence of a force - that force being the force of friction - which brings the book to a rest position. In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever!(Or at least to the end of the table top.)