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 * =Circular Motion=
 * The movement of an object at constant speed around a circle with fixed radius.
 * Axis -Straight line around which rotation takes place.
 * Rotation -Object turns around an internal axis. (Ex. ice skater)
 * Revolution -Object turns around an external axis. (Ex. Earth around the sun)
 * **Rotational Speed**
 * -Number of rotations per unit of time. (Ex. Carousel horse travel; same rotation speed but different tangential speed)
 * Linear Speed -Distance/Time.
 * Tangential Speed -Speed along a circular path.
 * Centripetal Force - Force that causes an object to follow a circular path.
 * =Newton and Gravity=
 * Isaac Newton believed that gravitation forces were responsible for the acceleration of objects on the moon and the earth.
 * Newton concluded that any two objects in the universe exert gravitational attraction on each other.
 * Newton's law of gravitational applies to ALL objects.
 * Universal gravitation and Distance.
 * As the distance separating two objects increases the force of attraction is exponentially smaller.
 * Fgrav = Gm1m2 / d2
 * G = Universal gravitation constant.
 * G = 6.67 x 10(-11) Nm2/Kg2
 * =Friction=
 * Friction is everywhere.
 * Ex. Needed to get a pencil to write.
 * Needed to do pretty much everything.
 * =Coulomb's Laws=
 * The relationship among electrical forces, charges, and distance.
 * Its like Newton's law of gravity. But, unlike gravity, electric forces can be attractive/repulsive.
 * Discovered by a French Scientist Charles Coulomb in the 18th century.
 * =Electric Fields=
 * -A vector quantity that relates the force exerted on a charge to the size of the charge.
 * The magnitude of the electric field is measured in N/C. (Newtons/Coulomb)
 * Direction of the arrows indicate the charge of the field.
 * Away from a positively charged object; toward a negatively charged object.
 * Strength of the field is denoted by the spacing between the lines. (Close = Strong)
 * Electric potential difference causes charges to move.
 * Grounding - Touching a body to earth to eliminate excess charge.
 * Electric Current - Flow of charged particles.
 * The flow will stop when the potential difference is zero; for current to continue to flow, an electrical force is needed.
 * Electrical Energy Sources
 * Voltaic or galvanic cells (dry cells) converts chemical to electrical energy.
 * A series of voltaic or galvanic cells connect together is called a battery.
 * Photovoltaic cell changes solar energy into electrical energy.
 * Generators convert kinetic energy into electrical energy.