An object's motion is the result of all forces acting on it.

*An object will stay at rest or continue constant velocity unless acted upon by an external unbalanced force.
*Unbalanced forces acting on an object cause changes in its velocity.
*Models (graphs) of an object's velocity versus time can be used to infer the presence or absence of unbalanced forces.
*There are four fundamental kinds of forces that exist in the universe: gravity, electromagnetism, and the two forces that hold the nuclei of atoms together.
*The gravitational force is an attractive force that depends on how much mass the objects have and how far apart they are.
*Mass is a measure of the amount of matter in an object and also measures an object's resistance to changes in motion.
*The magnitude of the gravitational force is weight (oz, lb, gm, Kg).
*Moving electric charges produce magnetic forces and moving magnets produce electric forces.
*Friction is an example of an electromagnetic force that opposes motion between two surfaces.
*Simple machines help accomplish a task with less effort by either changing the direction of motion or increasing the mechanical advantage.
*Mechanical advantage, using less force over a greater distance, allows the same work to be performed with less effort.

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