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BALANCING NAILS  (a challenge)

 

INTRODUCTION

We first learned about this activity from Pat McKean1 while visiting and teaching at her school.  This activity is appropriate for elementary school children in grades 3-6 and even into high school.  We use this activity after center of balance or center of gravity has been discussed.  We suggest that it be set up as a challenge for children and even for parents.  It is to be attempted over a period of time, perhaps a couple of weeks, and is to be tried at home as well as in the classroom.  It uses equipment that can easily be obtained and set up at home.  Tell children to bring to school a photograph or careful notes describing the final design to document their success.     
 

PURPOSE

The purpose of this activity is to get children and/or parents to construct a design that will give much practice applying center of balance or center of gravity and provide fun and challenge requiring considerable thinking, numerous trials, and many frustrations.
 

MATERIALS
 

1  block of wood, about 5" L x 5" W x 5/8" thick or larger, either board or plywood stock

12 or more identical common nails with heads, 10 penny or larger

 

PREPARATION FOR THE ACTIVITY

The purpose of the wood block is to hold one standing nail upright, with head upward, on a desk or table.  Elementary school children should have a teacher or parent prepare the wood block as follows.  Drill one hole into the center of the wood block, making certain that the axis of the hole is perpendicular to the face of the wood block.  The hole should be about 3/8" deep and have a diameter such that one of the nails just slides smoothly and snugly into the hole.  Drill test holes with several drills until you are sure that you have the right sized drill.  Put a piece of masking tape around the drill 3/8" up from the tip to show you clearly the correct depth.  The masking tape can be removed after drilling.
 

PROCEDURE

  1. Place the wood block flat on a desk or table.

  2. Put one nail upright, with head upward, in the drilled hole.  This is the standing nail, which must be vertical and stable, or the remainder of the activity will be exceedingly difficult.

  3. The challenge is to balance the remaining 11 nails on the standing nail.  To complete this activity successfully, none of the 11 nails may touch the wood block, the desk or table, or anything else that might help hold them up.  No additional equipment other than the wood block and the nails may be used.  Don't expect to finish this activity in five minutes.  Think of an idea, try it, try to figure out why it didn't work, and then think of a new idea.  Stop before you get too frustrated, think about the challenge at least overnight, and then come back to the activity a day or two later.  Discuss your ideas with your parents or siblings, and let them try the activity also.  If you are successful, take a photograph and/or write very detailed notes describing your successful design so that you can show these to your teacher.

 

EXPLANATION

 

If you are performing this activity directly from this web site rather than from an introduction in your classroom, or if you are a teacher wanting to check your design or one from your children, contact us by e-mail at scaifec@union.edu to see if your design is a legitimate one and for additional explanation. 
 

ADDITIONAL SUGGESTIONS

Any junk piece of wood including a piece of 2" x 4" will serve as the wood block.  Teachers or parents should drill the hole in the wood block.

There are probably several designs that will allow the additional nails to be balanced on the standing nail although we have found only one design that works consistently.  An elementary school teacher in the Pittsburgh area reported that her high-school-student son was able to balance 24 nails on the upright standing nail before the design collapsed!
 

REFERENCES

  1. Personal communication from Patricia B. McKean, Convent of the Sacred Heart, 1177 King St., Greenwich,  CT 06836.

 

Kids Involved Doing Science is at http://www.kids.union.edu     Modified 10/23/02 by C. & P. Scaife