30 points if you ask in 5 minutes why is it impossible to create a perpetual motion machine? energy will eventually be converted into heat and the machine will burn up. some of the energy will always be lost in the conversion and therefore it will eventually stop. the friction that exists within machines will eventually cause the levers to break. it is not impossible; perpetual motion machines already exist.

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 =