friction

• lovesgarfield

  26 Jul 10, 17:31

  Friction is independent of the area of contact. Does this mean when u drag an elephant across the road the friction is the same as when u drag an cockroach across the road?

  Thanks in advance for any expert clarification on this. 

• ^Acid^ aka s|aO^eH~

  26 Jul 10, 17:37

  Originally posted by lovesgarfield:

  Friction is independent of the area of contact. Does this mean when u drag an elephant across the road the friction is the same as when u drag an cockroach across the road?

  Thanks in advance for any expert clarification on this. 

  
  Nope...

  Friction is independent of area of contact... but it is dependent on the weight...

• eagle

  27 Jul 10, 08:14

  Originally posted by ^Acid^ aka s|aO^eH~:

  
  Nope...

  Friction is independent of area of contact... but it is dependent on the weight...

  Friction is not dependent on weight, but dependent on the magnitude of the reaction force between the ground and the object in question.

• monstersaurous

  4 Aug 10, 17:46

  Equation for friction:

  Friction = constant x N

  This constant is actually represented by the greek alphabet for 'm', otherwise pronounced as 'miu'.

  The value of the constant depends on the roughness of the 2 surfaces in contact - the rougher they are, the greater the value of the constant.

  'N' represents normal reaction force.  If you've got an elephant standing on the ground, the normal reaction force has a magnitude equal to the weight of the elephant.  If the elephant is standing inside a free falling elevator, the normal reaction force is zero.  If the elephant is standing inside an upward accelerating elevator, normal reaction force will be greater than the weight.

  So to answer your question - will the elephant and cockroach both experience the same amount of friction - yes, only if they have the same weight.  

• maskedangel

  4 Aug 10, 17:49

  Wow this is in depth.... Too much friction might cause abrasion..
• eagle

  6 Aug 10, 10:24

  Hi monstersaurous,

  the true equation for friction is

  f ≤ μR

  as you have said, R is the normal reaction force :)

  As for μ (pronounced as μ), it is called the coefficient of friction. The ≤ sign is because friction acts to oppose, up to the point of maximum friction where f = μR.

  For μ, we can further divide into μs and μk.

  μs is the coefficient of static friction, applicable when objects are stationary.
  μk is the coefficient of kinetic friction, applicable when objects are moving. The ≤ sign is not used.

  μs is always larger than μk because when moving, the atomic surfaces have yet to settle fully... Hard to explain with only words and no diagram...

• ~PEPPER~

  6 Aug 10, 10:32

  Chim and complex.