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Angle of Friction



(5) Angle of friction


  • It is the angle which the normal force N makes with the contact force when the equilibrium is limiting i.e when the condition of maximum Static friction is reached
  • Consider a block of mass "m" resting on a horizontal surface .Weight W=mg of this block is balanced by the normal force (N) of reaction as shown below in the figure.




    Angle of friction
    Mathematically
    W=mg=-N
  • if F is the contact force which each body exerts on the another body then this contact force can be resolved into two components
  • Perpendicular Components which is normal force N
  • Components parallel to the contact surface known as friction which is usually denoted by the fs,fk or fms
  • Angle BCD represented by λ is angle of friction
    Since N and fms are components of the contact force F,so we can write
    Fcosλ=N
    and Fsinλ=fms
    or we can say
    tanλ=fms/N
    Also from the definition of static friction we know that
    fmssN So tan λ=μs
    Thus we can conclude that coefficient of static friction is equal to the tangent of the angle of friction

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