1.A clean-earth trapezoidal channel with a bottom width of 1.8 m and a side surface slope 1:1 is to drain water uniformly at a rate of 8 m^3/s to a distance ok 1 km. If the flow depth is not to exceed 1.2 m, determine the required elevation drop. Manning number: n=0.022
2.What is the reason for the relatively high strength of wood in the longitudinal direction of the tree trunk as compared to the transverse direction ?
3.The de-carburization of a steel can also be described by the error fuction. Starting with the equation, (cx-c0)/(sc-c0) = 1-erf(x/(2*(sqrt(Dt)))), and taking cs=0 derive an expression to describe the concentration profile of carbon as it diffuses out of a steel with initial concentration c0.