Motion—Forces at Work position: a certain place relative to another object or the background; (tracing and measuring an object’s position over time can describe its motion) motion: a change of position; (unless acted on by a force, objects in motion tend to stay in motion and objects at rest remain at rest) inertia: any object stays still or moves in the same way until a force acts upon it frame of reference: the things around you that you can sense and use to describe motion speed: a measure of an object’s change in position during a unit of time; (how fast an object is moving); for example, 10 meters per second or 50 miles per hour; (a line graph can be used to show an object’s speed over time) force: a push or pull that causes an object to move, stop, or change speed or direction; (the greater the force, the greater the change in motion; the bigger the object, the less effect a force will have upon it) work: the use of a force to move an object; (moving an object a distance through space) Newton: the metric unit of force gravity: a force that pulls all objects toward each other friction: a force that keeps objects that are touching each other from sliding past each other easily; it is the resistance of motion; (friction creates heat) energy: the ability to cause a change; (exists in two states: kinetic or “motion energy” and potential or “stored energy”) kinetic energy: the energy of motion; (an object that is in motion) potential energy: stored energy; (an object that is NOT in motion) forms of energy: 1. Chemical – stored energy in matter (like in food or fuel) 2. Electrical – result of electricity (electrical energy can be transformed into heat, light or mechanical energy) 3. Mechanical – energy associated with the motion of an object through work (ex: can opener) 4. Solar – energy from the sun