A person is walking with constant speed vw, with respect to a moving sidewalk at O'Hare. He is walking in the same direction as the moving sidewalk which has speed vMs with respect to the stationary floor of O'Hare. The time it takes him to walk the length D of the moving sidewalk is tForward. For some unknown reason, once he gets off the moving sidewalk, he turns around and walks in the opposite direction of the moving sidewalk at that same constant speed vw with respect to the moving sidewalk, until he finally exits the moving sidewalk at his original entrance. The time it takes him to walk the length of the moving sidewalk on this return leg is tRack What is tForward in terms of vws ms, and D, as needed?

The inside surface of a cylindrical-shaped cave of inner diameter 1.0 m is continuously covered with a very thin layer of water. the cave is very long and it is open on both ends. the water on the cave surface is at a constant temperature of 15.5 °c. the cave is constantly exposed to wind such that 15.5 °c air flows through the cave at 4.5 m/s. the kinematic viscosity of the air is 14.66 x 10-6 m2/s and the molecular diffusion coefficient of water vapor in the air is 0.239 x 10-4 m2/s. because the cave diameter is so large, the flow of wind down the length of the cave, in the x direction, can be treated like it is external flow and the cave surface can be approximated as flat where appropriate. calculate the x value, in a) the transition to turbulent flow occurs at rex meters, where the air flow transitions from laminar to turbulent along the inside surface of the cave b) calculate the x value, in meters, where the bulk steady state concentration of water vapor in the air flowing in the cave is 10% of the saturation concentration. assume the air at the surface of the water layer is 100% saturated with water vapor. assume the wind entering the cave contained no moisture before it entered the cave. take into account the transition from laminar to turbulent flow when solving part b