ASAP 15 POINTS !! Is it important for engineers to define and compare the mechanical properties of different materials. Why?

At 12 noon, the count in a bacteria culture was 400; at 4: 00 pm the count was 1200 let p(t) denote the bacteria cou population growth law. find: (a) an expression for the bacteria count at any time t (b) the bacteria count at 10 am. (c) the time required for the bacteria count to reach 1800.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?

To design a steam turbine to produce 12,000 hp power. a engineer comsiders using a steady state stean low st 1160fr and engineer considers using a steady state steam flow at 1160°r and 450 psia to drive this steam turbine. the exhaust of the steam is cooled by the lake (vacuum). heat losing to the surroundings is measured at a rate of 555.55 btu/s. (a) sketch the system with the given conditions. (b) neglecting kinetic and potential energy changes from inlet to exit, determine the volumetric flow rate of the steam at the inlet, (ft'/hr). must clearly show unit conversions at crtical terms.