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Friction

December 8, 2016
Published By : Pratik Kataria
Categorised in:

Coefficient of Static Friction

$μ_s = {F_s}/{R}$ …For impending motion

Coefficient of Kinetic Friction

$μ_k = {F_k}/{R}$ For actual motion

R -> Magnitude of normal reaction

Angle of Friction

φ = $tan^{-1} μ $

For impending motion the angle between normal reaction and resultant reaction is called as angle of static friction.

For actual motion when P = $F_k$ the angle between normal reaction and resultant reaction is called angle of kinetic friction.

Angle of Respose

Angle of inclined plane with horizontal at which body is just on verge of sliding (impending motion) and so $F_s$ = $μ_s$ R
Angle of respose is denoted by α.


Note: $ ϕ_s$ = α

${\text"Tight side"}/{\text"Slack side"} = e^{μ_s β}$


Lap angle or angle of contact β must be in radians.

Above relation is used only when belt is about to slip.
Tight side represents the larger tension in part of belt which pulls and slack side represents the smaller tension in part which resists.

For V-belt ${T_1}/{T_2}$ = $e^{(μ_s β cosec α/2)}$

Band Brake

Breaking Torque $T_B$ = $(T_1 – T_2) r$