Draining the Swimming Pool

William Byrne Martin Luther King
4445 S. Drexel
Chicago, Il. 60653
312-536-8680

Objectives:

1. To determine the time needed to drain a quantity of water using tubes of
different inside diameters (I.D.)

2. To determine the time needed to drain a quantity of water using two tubes
at the same time, contrast this with the theoretical values and give
explanations for the differences.

Materials needed:

Stopwatch, 3 one gallon jugs, two plastic tubes about 3 feet long of
different inside diameter, plastic tray, water pails, hand calculators.

Strategy:

On a table place 3 one gallon jugs filled with water. Ask the class to
estimate how long it will take to drain one jug using a plastic tube of 1/4" I.D.
Show them this tube. Then, using the siphon method, drain one of the jugs using
the tube. This will be timed by someone in the class using the stopwatch. Next,
find the time according to the formula - V = (2gh)1/2At. Ask someone in the Physics
department about using this formula. Find "t" using the formula. Discuss
differences from the experimental value. Go through the same process using the 1/2"
tube. Again find the experimental value and the theoretical value and discuss the
differences. Finally, using the third jug of water and both tubes, find out how
long it takes to drain the jug of water. Then compare this time with the value
given by the algebraic formula for the problem.

Conclusions:

Discuss differences between theory and experiment. How could the two values
be brought closer together in this experiment? Discuss the role of friction.