The initial ultimate bod after mixing of the bergelmir river is 12.0 mg · l−1. the do in the bergelmir river after the wastewater and river have mixed is at saturation. the river temperature is 10◦ c. at 10◦ c, the deoxygenation rate constant (kd) is 0.30 day−1 , and the reaeration rate constant (kr) is 0.40 day−1 . determine the critical point (tc) and the critical do. tc = 2.88 days. critical do = 7.53 mg · l−1

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.

Water at 70°f and streams enter the mixing chamber at the same mass flow rate, determine the temperature and the quality of the exiting stream. 0 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. if both streams enters the mixing chamber at the same mass flow rate, determine the temperature and the quality of the existing system.

Calculate the bore of a cylinder that has a stroke of 18 inches and an extension time of 6 seconds at a flow rate of 4 gal/min.