Auniform circular disc of mass m and radius a can rotate freely in a vertical plane about a fixed axis through its centre. a light string attached to a point on the rim is wrapped round the rim of the disc with part of the string left hanging vertically. find the angular velocity generated from rest when the string is pulled with a constant vertical force f for a time t

Consider the growth of a 20-nm-diameter silicon nanowire onto a silicon wafer. the temperature of the wafer surface is maintained at 2400 k. assume the thermal conductivity of the silicon nanowire is 20 wm-1k-1 and all its surfaces including the tip are subjected to convection heat transfer with the coefficient h = 1×105 wm-2k-1 and t∞ = 8000 k. when the nanowire grows to l = 300 nm, what is the temperature of the nanowire tip (t (x =