Let ρ be the mass per unit length of the chain Ρ = m / l or , m = ρl Weight of hanging part = W2 = ρlg Weight of chain over the table = W1 = ρ ( L-l ) g For equilibrium , R = ρ ( L-l ) g --------------- ( i ) f = W2 = ρlg μR = ρlg -------------------( ii ) ( i ) Divided by ( ii ) gives 1 / μ = ( L-l )/ l l = μL – μl l + μl = μL Therefore , l = μL /( μ + 1 ) Friction- A boon or Bane against motion Friction is a boon because of its advantages like :
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Friction helps in walking