A roller coaster car of mass 90 kg has two people seated in it whose combined mass is 130 kg. If the height of point A from the ground is 80.0 m, determine the potential energy of the car with the people in it at A. 172 kJ
70.6 kJ
17.6 kJ
86.2 kJ

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 =