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?

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 the velocity diagram shown below, $$u=$$ blade velocity, $$C=$$ absolute fluid velocity and $$W = $$ relative velocity of fluid and the subscripts $$1$$ and $$2$$ refer to inlet and outlet.

A vapor absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of $$100$$ $$W$$ is required at $$250$$ $$K$$ when the heat source available is at $$400$$ $$K.$$ Heat rejection occurs at $$300$$ $$K.$$ The minimum value of heat required (in $$W$$) is