A 20 kg metal block is placed on a horizontal surface. The block just begins to slide when horizontal force of 100 N is applied to it.
Calculate the coefficient of static friction. If coefficient of kinetic friction is 0.4, then find minimum force to maintain its uniform motion.
Given: m = 20 kg, FL = 100 N, μk = 0.4
To find:
i. Coefficient of static friction (μS)
ii. Minimum force required (Fk)
Formulae:
i. μs = \(\frac{F_L}{N}=\frac{F_L}{mg}\)
ii. μS = \(\frac{F_K}{N}\)
Calculation:
From formula (i),
μs = \(\frac{100}{20\times9.8}\) = 0.5102
From formula (ii),
Fk = μkN = μk × mg = 0.4 × 20 × 9.8
∴ Fk = 78.4 N
1. The coefficient of static friction is 0.5102.
2. The minimum force required is 78.4 N.