A boy pushes a lever down 2 meters with a force of 25 newtons. The box at the other end with a weight of 50 newtons moves up 2.5 meters. a. Calculate the work input by the boy

Winput = Fd

b. Calculate the work output on the box

Woutput = Fd

c. Calculate the percentage efficiency of the lever.

Efficiency = (Woutput/Winput)100%

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 =