A line of traffic moving at 30 mi/h and a concentration of 50 veh/mi is stopped for 30s at a red light. Calculate

(a) the velocity and direction of the stopping wave
(b) the length of the line of cars stopped during 30s of red, and
(c) the number of cars stopped during the 30s of red. Assume a jam concentration of 250 veh/mi.

Estimate the change in specific internal energy au and specific enthalpy h from inlet to outlet for ethylene glycol (a liquid) flowing through each of the following devices: (a) a heat exchanger where the glycol temperature increases from 20 °c to 80 °c; (b) a pump operating at about 25 °c and increasing the glycol pressure from 100 kpa to 8 mpa.