Subtopic: Design and selection of machine elements – gears, pulleys, chains and sprockets and belts
Question Statement:
A flat leather belt with 9 × 250 mm cross section is used to drive a cast iron pulley of diameter 0.90 m running at 336 rpm. The active arc of contact on the smaller pulley is 120°. The belt weighs 980 kg m⁻³. Coefficient of friction between the leather and cast iron is 0.35. Centrifugal tension experienced by the belt is
Options:
(A) 5.5 N
(B) 56.4 N
(C) 552.8 N
(D) 2211.2 N
Official Answer Key:
C
Step-by-Step Solution & Explanation
Belt speed, v = πDN/60 = π(0.90)(336)/60 = 15.834 m/s. Mass per unit length, m = ρ×(cross-section area) = 980×(0.009×0.250) = 2.205 kg/m. Centrifugal tension, T_c = m·v² = 2.205×(15.834)² = 552.8 N (arc of contact/μ are not needed for T_c itself — they're distractor data for a follow-up power/tension calc).
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