39) If a room is to be maintained at 200K while surroundings are 300K by a refrigeration system using reversed Carnot cycle, Coefficient of Performance (COP) will be

40) A differential manometer connected at two points shows a difference in mercury level as 10cm. The difference of pressure at the two points are: (Assume pipe is horizontal, Specific gravity of mercury is 13.6 and fluid in pipe is 0.9, g=10m/square seconds)

41) A steel rod of 1 m length has to transmit a force of 15 kN without stretching more than 1mm. E of steel is 200Gpa. Minimum cross sectional area required is

42) A thin cylindrical shell of diameter (d), length (l), and thickness (t) is subjected to an internal pressure (p). The ratio of the longitudinal strain to hoop strain is

43) Rankine's constant for a mild steel column with both ends hinged is