1. The problem statement, all variables and given/known data A colliery lift cage can be considered as a simple hoist system. An investigation found that when raised from the bottom of the mineshaft, the cage accelerates uniformly for 10 seconds, travels for 70 seconds at constant speed of 3 m/s and just before reaching the pit head, decelerates uniformly in 4 seconds. Frictional torque at the drum shaft is constant at 1500 Nm. Mass of drum = 1.5 Tonne Dia. = 3m k = 1.4m Mass of Cage = 0.5 Tonne For the period during which the cage accelerates, determine: (i) The tension in the cable with a labelled free body diagram (assume that the mass of the cable is negligible.) (ii) The torque required at the drum shaft. 2. Relevant equations a = Δv/t ∑F = ma ∑τ = Iα I = mk^2 3. The attempt at a solution Acceleration calculated to be 0.3m/s^2. Tension in cable: ∑F = ma ∴ T = m(a + g) = 5055N (correct according to answer sheet) ∑τ = Iα I = mk^2 = 2940kgm^2 α = a/r = 0.2m/s^2 ∴τ = Iα + τƒ + Tr, where τƒ = frictional torque of 1500Nm and Tr = 7582.5Nm = 9671Nm The answer given is 8171Nm -- which is simply the above calculation without consideration to the constant frictional torque of 1500Nm. Am I missing something or is the answer given simply incorrect? Thanks for any help!