Lyvonia Hearns - Asa Philip Randolph 

Building A Straw Power Tower 
 
Lyvonia Hearns                 Asa Philip Randolph 
                               7316 S. Hoyne 
                               CHICAGO IL 60619
                               (773) 535-9015

Objective(s):

 To explore the effects of shape, materials, and balance in building a Straw 
Power Tower that can support the most pennies.  Towers must be at least 58cm 
(23in.) tall. This  activity is for students in grades 2-8.  Divide the class 
into teams of 5 or less. 

Materials Needed:          
    
    Per Team       
 Lab Report            Contest Rules  50 Glad straight straws 
 hole punch            many pennies   120 small metal paper clips 
 2 large paper clips   scissors       5 clean, empty 1-pint milk or juice cartons
 measuring stick       table, desk, or floor       

Strategy:

 Set aside 15 straws from the 50 you were given.  With your team begin to build 
a Tower from your straws and paper clips.  It can be any shape you want, but you 
can't use any other materials.  Stop building when your 15 straw tower stands up 
by itself.  Make a Weight Basket out of the 1-pint milk carton.  Use the large 
paper clips to attach the weight basket to the tower.  The Basket must not touch 
the ground or floor.  Slowly add 20 pennies to your Weight Basket.  Where does 
your tower sag or bend?  If you need to, add more pennies or jiggle the basket. 
Could these weak spots collapse under more weight?  Remove your Weight Basket. 

List Your Variables

Pick one weak spot on your Tower.  What change could make the weak spot 
sturdier?  Anything you could change on your Tower is a variable.  Now with your 
team make a list of changes that might improve your Tower in general.  Some 
variables to think about are:     

Shape- Could you make a square or polygon (many sided shape) into triangles to 
make it stronger?

Strength- of beams- Could you combine 2 or more straws to make a beam
stronger?

Length of straws- Could some beams be longer?  Should some be shorter (cut 
straws) 

Joints- Are there other ways to connect the straws?

Locations of strong beams- Should the strongest beams be near the top of the 
tower or the bottom?

Size of foundation (base)- What effect does changing the size of the foundation  
have on your Tower?

Location of Weight Basket- Does it matter where you attach the Weight Basket? 
(The bottom must be at least 20cm (8in) off the ground.) 

MAKE A CHANGE

Choose one variable from your list.  Make the change to a weak spot on your 
Tower.  Make one change at a time.  (For ex., if you change to longer beams, 
don't also change the size of the foundation.)  Why is it important to change 
only one variable at a time?  Record the variable you changed on your lab report 
next to "15-Straw Tower" Now test your change.  Attach the Weight Basket to the 
exact same spot as before.  Add 20 pennies and observe your Tower.  Did the 
change make the weak spot sturdier?  Record the results. 

Keep Building 

Set aside 15 more straws from your 50.  Continue to build and strengthen your 
Tower.  After these 15 straws have been added, test your Tower with a Strength 
Test as before.  Then change one variable that could make the weak spot 
stronger.  Add the last 20 straws to your Tower.  Repeat the Strength Test.  
Make the final changes until your team is satisfied with your Tower's strength, 
shape, weight Basket attachment, and height. 

Performance Assessment:

 Name your Tower.  Measure, record, and sign off its official height on your lab 
report.  Gently add pennies to the Weight Basket, counting one by one.  How many 
can the Tower support before the Weight Basket hits the table?  Enter your penny 
count on your lab report.  Now write a paragraph on the back of your lab report. 
List the features that made your Power Tower strong, explaining how each helped 
the Tower's weak points.  Describe your Tower's weak points.  What made it 
finally collapse?

Conclusions:

  Display your Straw Power Towers around your classroom.  ENJOY!

References:

Super Science Nov./Dec. 1998