Draining the Swimming Pool

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

Objectives: 

For 9th and 10th grade

 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.