A little boy rides a roller coaster that makes a loop with a radius of 30.0m. The boy hits the bottom of the loop traveling at 40.0m/s. The net force on the boy is 1350N. What is the mass of the boy? 1800 kg
60 kg
1010 kg
25.3 kg

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 =