Find the solidification time of the two iron castings when both are poured (with no superheats) into the sand molds at initial temperature 28°C.

(i) A slab shaped casting of 10 cm thickness, (ii) a sphere of 10 cm in dia. Iron: freezing temp: 1540°C; L= 272 kJ/kg; density = 7850 kg/m3 Sand: c = 1.17 kJ/kg-K; k = 0.865 W/mk; density = 1600 kg/m3

An engine, weighing 3000 n, is supported on a pedestal mount. it has been observed that the engine induces vibration into the surrounding area through its pedestal at the maximum operating speed. determine the stiffness of the dynamic vibration absorber spring in (n/m) that will reduce the vibration when mounted on the pedestal. the magnitude of the exciting force is 250 n, and the amplitude of motion of the auxiliary mass is to be limited to 2 mm note: in this question type-in right numbers, no decimals, no fractions, no unit. approximate to right number if needed