Friction - GCSE Physics PDF

FR I C T I ON  OBJECTIVES NAME THE DIFFERENT KINDS OF FRICTION DESCRIBE EACH KIND OF FRICTION IDENTIFY THE FACTORS AFFECTING FRICTION CALCULATE WORD PROBLEMS ABOUT FRICTION REVIEW ANY FORCE THAT RESISTS MOTION IT INVOLVES OBJECTS THAT ARE IN CONTACT WITH EACH OTHER. THIS IS THE FORCE THAT K...

FR I C T I ON  OBJECTIVES NAME THE DIFFERENT KINDS OF FRICTION DESCRIBE EACH KIND OF FRICTION IDENTIFY THE FACTORS AFFECTING FRICTION CALCULATE WORD PROBLEMS ABOUT FRICTION REVIEW ANY FORCE THAT RESISTS MOTION IT INVOLVES OBJECTS THAT ARE IN CONTACT WITH EACH OTHER. THIS IS THE FORCE THAT KEEPS AN OBJECT FROM SLIDING DOWN AND INCLINE PLANE.  FRICTION IS A FORCE THAT FRICTION RESISTS THE MOTION OF TWO SURFACES THAT ARE TOUCHING. WHEN A MOVING OBJECT COMES IN CONTACT WITH ANOTHER OBJECT, FRICTION IS THE OPPOSING FORCE THAT SLOWS OR STOPS THE MOVING OBJECT. TYPES OF FRICTION STATIC-PREVENTS OBJECTS SLIDING SLIDING-RESISTS OBJECTS WHILE THEY ARE MOVING FLUID…AIR OR WATER EXAMPLES OF FRICTION TIRES ON THE ROAD WALKING/RUNNING NAILS INTO WOOD SLED ON HILL  WITHOUT FRICTION, AN OBJECT WOULD CONTINUE TO MOVE AT CONSTANT SPEED FOREVER. THE STRENGTH OF THE FORCE OF FRICTION DEPENDS ON THE TYPE OF SURFACES AND HOW HARD THE SURFACES PUSH TOGETHER. ROUGH SURFACES PRODUCE GREATER FRICTION THAN SMOOTH SURFACES. PRINCIPLES OF FRICTION FRICTION ACTS PARALLEL TO THE SURFACE THAT ARE IN CONTACT. THE DIRECTION THAT FRICTION ACTS IS OPPOSITE THE DIRECTION OF THE MOTION (OR INTENDED MOTION).Fnormal Ffriction(k) Fapplied Fweight SLIDING FRICTION A RESISTANCE TO MOVEMENT THAT IS CREATED WHEN TWO THINGS RUB TOGETHER. FLUID FRICTION THE FORCE THAT TRIES TO SLOW OBJECTS DOWN WHEN THEY MOVE THROUGH A LIQUID OR A GAS. IT'S ALSO KNOWN AS "DRAG", OR "AIR RESISTANCE". ALL GASES AND LIQUIDS ARE FLUIDS. AN AIRPLANE AND A SWIMMER BOTH EXPERIENCE FLUID FRICTION.  ICE BREAKER The ________ the surface, the greater the _________. Friction also produces ________. If you rub your hands together ________, they will get warmer. friction heat quickly rougher Can you complete the sentences with these words?  rougher the surface, the greater the _________. The ________ friction Friction also produces ________.heat If you rub your hands together ________, they will get warmer. quickly friction heat quickly rougher Were you correct? STATIC FRICTION – THE FRICTIONAL FORCE PRESENT JUST BEFORE MOTION BEGINS. STARTING FRICTION IS WHEN STATIC FRICTION IS AT IS MAXIMUM. KINETIC FRICTION – THE FRICTIONAL FORCE PRESENT WITH MOTION NOTE: STATIC FRICTION IS USUALLY HIGHER THAN KINETIC FRICTION  FRICTION Ffr = m Fn μ is called coefficient of friction  m has no units ¨ depends on characteristics of both surfaces ¨ Higher m = rougher surface / more friction motion Note: friction Friction does NOT depend on the surface area of contact FRICTION PROBLEMS – WE DO A 28 KG CRATE INITIALLY AT REST ON A HORIZONTAL FLOOR REQUIRES A 75 N HORIZONTAL FORCE TO SET IT IN MOTION. FIND THE COEFFICIENT OF STATIC FRICTION BETWEEN THE CRATE AND THE FLOOR. WHAT DO WE DO FIRST?  FRICTION A 28 KG CRATE INITIALLY AT REST ON A PROBLEMS HORIZONTAL FLOOR REQUIRES A 75 N HORIZONTAL FORCE TO SET IT IN MOTION. FIND THE COEFFICIENT OF STATIC FRICTION BETWEEN THE CRATE AND THE FLOOR. REMEMBER OUR STRATEGY: 1)DRAW A FREE BODY DIAGRAM 2)IDENTIFY ALL VARIABLES AND THE UNKNOWN 3)IDENTIFY RELEVANT EQUATIONS 4)SOLVE!  FRICTION PROBLEMS A 28 KG CRATE INITIALLY AT REST ON A HORIZONTAL FLOOR REQUIRES A 75 N HORIZONTAL FORCE TO SET IT IN MOTION. FIND THE COEFFICIENT OF STATIC FRICTION BETWEEN THE CRATE AND THE FLOOR. FRICTION A FORCE OF 40.0 N PROBLEMS ACCELERATES A 5.0-KG BLOCK AT 6.0 M/S2 ALONG A HORIZONTAL SURFACE. A. HOW LARGE IS THE FRICTIONAL FORCE? B. WHAT IS THE COEFFICIENT OF FRICTION?  FRICTION APROBLEMS FORCE OF 40.0 N ACCELERATES A 5.0-KG BLOCK AT 6.0 M/S2 ALONG A HORIZONTAL SURFACE. A. HOW LARGE IS THE FRICTIONAL FORCE? B. WHAT IS THE COEFFICIENT OF FRICTION? FRICTION PROBLEMS A 12 KG SUITCASE IS PUSHED WITH A FORCE OF 38 N TO THE LEFT. IF THE COEFFICIENT OF KINETIC FRICTION BETWEEN THE SUITCASE AND THE FLOOR IS 0.3, HOW FAR WILL THE SUITCASE MOVE AFTER 5 SEC?