If an aluminum plate 4 mm thick is mounted in a horizontal position, and its bottom surface is well insulated. a special, thin coating is applied to the top surface such that it absorbs 80% of any incident solar radiation, while having an emissivity of 0.25. the density p and specific heat c of aluminum are known to be 2700 kg/m3 and 900 j/kg k, respectively. (a) consider conditions for which the plate is at a temperature of 25 c and its top surface is suddenly exposed to ambient air at t=20 c and to solar radiation that provides an incident flux of 900 w/m2 . the convection heat transfer coefficient between the surface and the air is h = 20 w/m^2 k. what is the initial rate of change of the plate temperature?

On a average work day more than work place firs are reorted

Different types of steels contain different elements that alter the characteristics of the steel. for each of the following elements, explain what the element does when alloyed with steel.

Tom is having a problem with his washing machine. he notices that the machine vibrates violently at a frequency of 1500 rpm due to an unknown rotating unbalance. the machine is mounted on 4 springs each having a stiffness of 10 kn/m. tom wishes to add an undamped vibration absorber attached by a spring under the machine the machine working frequency ranges between 800 rpm to 2000 rpm and its total mass while loaded is assumed to be 80 kg a) what should be the mass of the absorber added to the machine so that the natural frequency falls outside the working range? b) after a first trial of an absorber using a mass of 35 kg, the amplitude of the oscillation was found to be 10 cm. what is the value of the rotating unbalance? c) using me-3.5 kg.m, find the optimal absorber (by minimizing its mass). what would be the amplitude of the oscillation of the absorber?