There are four samples P, Q, R and S, with natural frequencies 64, 96, 128 and 256 Hz, respectively. There are mounted on test setups for conducting vibration experiments. If a loud pure not of frequency 144Hz is produced by some instrument, which of the samples will show the most perceptible induced vibration?

In a spring-mass system, the mass is 0.1 kg and the stiffness of the spring is 1 kN/m. By introducing a damper, the frequency of oscillation is found to be 90% of the original value. What is the damping coefficient of the damper?

The following table of properties was printed out for saturated liquid and saturated vapour of ammonia. The titles for only the first two columns are available. All that we know is that the other columns (columns $$3$$ to $$8$$) contain data on specific properties, namely, internal energy $$(kJ/kg),$$ enthalpy $$(kJ/kg)$$ and entropy $$(kJ/kg.K).$$

The specific enthalpy data are in columns

The following table of properties was printed out for saturated liquid and saturated vapour of ammonia. The titles for only the first two columns are available. All that we know is that the other columns (columns $$3$$ to $$8$$) contain data on specific properties, namely, internal energy $$(kJ/kg),$$ enthalpy $$(kJ/kg)$$ and entropy $$(kJ/kg.K).$$

When saturated liquid at $${40^ \circ }C$$ is throttled to $$ - {20^ \circ }C,$$ the quality at exit will be