The town of Pittsburg discharges 0.126 m3 /s of treated wastewater into Cherry Creek. The BOD5 of the wastewater is 34 mg/L. Cherry creek has a flow rate of 0.126 m3 /s. The BOD5 of the river before the wastewater outfall is 1.2 mg/L. The BOD rate constants are 0.222 and 0.090 d-1 for the wastewater and creek respectively. The temperature of the creek and wastewater is 20 C. Calculate the initial ultimate BOD after mixing. (Problem 7-24 from textbook)

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false

An air conditioning system consist of a 5 cm diameter pipe, operating at a pressure of 200 kpa. the air initially enters the pipe at 15°c with a velocity of 20 m/s and relative humidity of 80%. if the heat supply throughout the process is 960 w, determine the relative humidity and the temperature at the outlet