Newton's First Law

1. Force is a push or pull exerted on an object.
2. Forces are described not only by how strong they are, but also by the direction in which they act.
3. Forces can be combined.
   1. When two or more forces act in the different directions, they add together, but it’s like adding a positive and negative number.
4. Equal forces acting on one object in opposite directions are called balanced forces.
   1. Balanced forces acting on an object will not change the object’s motion.
5. The overall force on an object after all the forces are added together is called the net force.
6. When there is a net force acting on an object, the forces are said to be unbalanced.
   1. Unbalanced forces can cause an object to start moving, stop moving, or change direction.
   2. Unbalanced forces acting on an object will change the object’s motion (causes acceleration).  

1. Force is needed only to change the motion of an object.
2. Whether an object is moving or at rest, every object resists any change to its motion.
   1. Inertia is the tendency of an object to resist change in its motion.
3. Newton’s first law of motion states than an object at rest will remain at rest, and an object that is moving at a constant velocity will continue moving at constant velocity unless acted upon by an unbalanced force.
4. Newton’s first law of motion is also called the law of inertia.

1. Mass is the amount of matter in an object.
2. The SI unit of mass is the kilogram (kg).
3. The amount of inertia an object has depends on its mass.
4. The greater the mass of an object, the greater its inertia