Tag: science & technology

G. Madhavan Nair served as Chairman of ISRO from 2003 to 2009, overseeing missions like Chandrayaan-1. K. Kasturirangan (option A, misspelled) was his predecessor. A. P. J. Abdul Kalam was a former ISRO chairman but not current in the exam's timeframe. Rakesh Sharma is a cosmonaut, not ISRO chairman.

G. Madhavan Nair served as Chairman of ISRO from 2003 to 2009, overseeing missions like Chandrayaan-1. K. Kasturirangan (option A, misspelled) was his predecessor. A. P. J. Abdul Kalam was a former ISRO chairman but not current in the exam's timeframe. Rakesh Sharma is a cosmonaut, not ISRO chairman.

Aryabhatta, launched in 1975, was India's first satellite. Rohini was a later series, Bhaskara 1 and 2 were experimental remote sensing satellites launched after Aryabhatta.

Hydrostatic bearings use an external pressure source to create a fluid film, making them ideal for very heavy loads at slow speeds. Hydrodynamic bearings rely on relative motion and are better for higher speeds. Ball and roller bearings have load limitations compared to fluid film bearings.

A key in mechanical assembly fails by both crushing (compressive stress from the shaft) and shearing (transverse shear stress). The combined stress state makes it susceptible to both failure modes simultaneously, which is why key design considers both crushing and shear stresses.

Sodium has the highest thermal conductivity among liquid metals at approximately 142 W/(m·K), which is why it's used as a coolant in nuclear reactors. Mercury has relatively low thermal conductivity (~8.3 W/(m·K)), and both potassium and lead are also lower than sodium.

A radiation shield works primarily by reflecting radiation away, so high reflectivity is essential. Materials with high reflectivity (like polished metals or multilayer insulation) are most effective at blocking thermal radiation.

A hydrometer is an instrument that measures the specific gravity (relative density) of liquids. It floats at different levels depending on liquid density, giving a direct reading of specific gravity. It's commonly used to test battery acid concentration, urine density, and alcohol content in beverages.

Up to the critical radius of insulation, adding insulation actually increases heat loss for cylindrical systems like pipes. This counterintuitive result occurs because the increased outer surface area (which increases convection) outweighs the insulation's resistance to conduction. Only beyond the critical radius does insulation reduce heat loss.

The critical damping coefficient Cc = 2√(km), which depends only on mass (m) and stiffness (k). Critical damping is the threshold between oscillatory and non-oscillatory response in a second-order system, determined solely by these system parameters.