EQUILIBRIUM OF FORCES AND FRICTION

EQUILIBRIUM

THE STATE IN WHICH THERE IS NO CHANGE IN THE MOTION OF A BODY

EQUILIBRIUM

THIS CONDITION EXISTS WHEN THE VECTOR SUM OF THE FORCES TENDING TO PRODUCE TRANSLATION OR MOTION IN A STRAIGHT LINE IS ZERO

EQUILIBRIUM

THIS CONDITION EXISTS WHEN THE ALGEBRAIC SUM OF THE MOMENTS TENDING TO ROTATE THE BODY IS ZERO

FREE-BODY DIAGRAM/FORCE DIAGRAM

IS AN ISOLATED VIEW OF A BODY WHICH SHOWS ONLY THE EXTERNAL FORCES EXERTED ON THE BODY

CONTACT FORCES, FIELD FORCES

THE TWO TYPES OF FORCES WHICH ACT ON A BODY

WEIGHT

THIS GRAVITATIONAL ATTRACTION ON A BODY BY THE EARTH DOES NOT HAVE A POINT OF CONTACT WITH THE BODY

DOWNWARD

THE DIRECTION OF THE WEIGHT VECTOR ALWAYS BE ASSUMED TO BE ___

FRICTION

REFERS TO THE RESISTANCE TO MOTION THAT OCCURS WHENEVER TWO MATERIALS OR MEDIA ARE IN CONTACT WITH EACH OTHER

FRICTION

MAY BE DEFINED AS THE CONTACT RESISTANCE EXERTED BY ONE BODY UPON A SECOND BODY WHEN THE SECOND BODY MOVES OR TENDS TO MOVE FAST

FRICTION

THIS RESISTANCE OCCURS IN ALL TYPES OF MEDIA: SOLIDS, LIQUIDS, AND GASES

STATIC, SLIDING (KINETIC), ROLLING

TYPES OF FRICTION BETWEEN SOLIDS

STATIC FRICTION

INCLUDES ALL CASES IN CHICH THE FRICTIONAL FORCE IS SUFFICIENT TO PREVENT RELATIVE MOTION BETWEEN SURFACES

SLIDING/KINETIC FRICTION

OCCURS WHEN THERE IS RELATIVE MOTION AT THE INTERFACE OF THE SURFACES IN CONTACT

ROLLING FRICTION

OCCURS WHEN ONE SURFACE ROTATES AS IT MOVES OVER ANOTHER SURFACE