Example
Metal can be cut by using an oxyacetylene torch. During the process, oxygen is supplied via a pressurized tank (30 cm in dia. And 1 m tall). A valve is used to maintain the oxygen flowing out at a constant velocity of 2 m/s. The valve has an opening area of 10-4 m2 and the temperature inside the tank is unchanged and equal to 25°C. If the initial pressure inside the tank is 10,000 kPa gage, how long will it take to drain the tank such that the pressure is 90% of its initial value.