Rosita is planning an investigation to determine how a lifeboat's shape affects its ability to carry passengers. She notices she has made an error in her data table
below. What does she need to change in her table to make her investigation a
controlled experiment?
Boat
Size and area of aluminum
foil
10 cm x 30 cm = 300 cm?
Shape of boat
1
rectangular
2
10 cm x 30 cm = 300 cm?
oval
3
20 cm x 30 cm = 600 cm?
square
4
20 cm x 30 cm = 600 cm?
triangular

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?

Air enters a horizontal, constant-diameter heating duct operating at steady state at 290 k, 1 bar, with a volumetric flow rate of 0.25 m°/s, and exits at 325 k, 0.95 bar. the flow area is 0.04 m2. assuming the ideal gas model with k = 1.4 for the air, determine (a) the velocity at the inlet and exit, each in m/s, and (c) the rate of heat transfer, in kw flow rate, in kg/s, (b) the mass kg 0.3

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.