The Tank Draining Exercise
Apparatus
Figure 1 is a schematic of the equipment used in the tank-draining exercise. The focus of the exercise is on two cylindrical tanks, one with straight walls (single diameter) and another with a step-shaped wall (two diameters). A pressure transducer mounted on the side of each tank, and at a distance H from the base. A DC power supply provides the electrical excitation for the transducer
The pressure transducers are connected to a USB-based data acquisition device (NI USB-6008 from National Instruments), which digitizes the signals and transmits the digitized data to a computer.
Not shown in the schematic is a digital camera mounted on a tripod. The camera captures images of the water jet that flows from a hole in the side of the tank.
Figure 1: Equipment used in the tank draining exercise.
Figure 2 is a photograph of the step-walled tank. The pressure transducer is attached to one side of the tank. On the opposite side of the tank are three holes at the same depth at the pressure transducer. Green food coloring was added to the water in order to make the water more visible in the photograph.
The tank is rests on a base, which has a meter stick rigidly mounted in a horizontal position. There are numerous bubbles in the lower section of the tank, but the bubbles do not affect the measurements made during the exercise.
Figure 2: Step-walled tank with pressure transducer attached to the left side and a stopper in the hole in the right side. The water is dyed with green food coloring to make it easier to see in the photograph.
Figure 3 is a photograph of the tank as water is draining from the hole in the side. The water jet emerges from the hole in the side of the tank. The horizontal distance traveled by the jet is measured with the meter stick fixed to the base of the apparatus. A clear measuring tape is attached to the side of the tank. That tape is used during the tank-filling exercise.
Figure 3: Step-walled tank during draining. The water is dyed with green food coloring to make it easier to see in the photograph.
Lab Exercise
The guided-inquiry laboratory exercise takes about one and a half hours. The laboratory worksheet contains instructions for completing steps of the experiment. It also contains questions that require experimental investigation to answer.
