1. Newton’s First Law of Motion
Forces
Newton’s First Law of Motion

2. Balanced and unbalanced forces
The combination of all forces acting on an object is called the net force
The net force determines whether an object moves and in what direction and acts in the direction of the greater force
A net force acting on an object is always unbalanced and can cause an object to start or stop moving
Only an unbalanced force can change the motion of an object
If the net force on an object is zero, the forces acting on the object are balanced; the motion of the object does not change

4. Newton’s First Law of motion
In the early 1600s, Galileo suggested that once an object is in motion, no force is needed to keep it moving; force is needed only to change the motion of an object or stop the motion of an object that is already moving
Newton’s 1st law states: an object at rest will remain at rest, and an object in motion will remain in motion, unless acted on by an outside, unbalanced force (law of inertia)
Inertia is the resistance of an object to a change in the speed or direction of its motion; closely related to mass
The greater the mass of an object, the greater its inertia and the greater the force required to change its motion