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Center of Mass Exploration

LEGO Smart Creativity Contest Entry
By Ian Durham, Saint Anselm College

In order to assist activity leaders in using this activity, a URL leading to a PDF that includes some basic pictures is listed at the end of the following description. 1. Students begin with the 8x2 brick and the single 1x1 brick.  Initially they mount the 1x1 piece directly under the 8x2 in the dead center and set it on a table.  It should stand on its own without leaning (barely).  Note that this means the single 1x1 piece should be placed into one of the holes under the 8x2 piece. 2. Next, have the students mount a 6x2 piece crosswise on the end of the top of the 8x2 piece.  The constructed piece should no longer balance.  Students should now experiment with the 1x1 piece, moving it around among the seven holes pictured above until they find a location at which it balances when set on the table. Question for students: Did you ahve to move the smaller piece toward the 6x2 piece or away from it? Why do you think that is?  Note to teacher: Assemble led structure should balance with the 1x1 piece in the third hole from the right. 3. Students should then add a second 6x2 piece on top of the first.  They will once again find that they need to move the small 1x1 piece in order for the whole thing to balance. Note to teacher: Assembled structure should balance with the 1x1 piece in the second hole from the right. 4. Next, students will need the following pieces: the 1x1 piece again, the thin 4x4 piece, two regular 4x2 pieces, and two regular 2x2 pieces.  Students should mount one 4x2 piece and one 2x2 piece on top of the 4x4 slab such that they form an L.  The second 4x2 piece should be mounted on top of the first with the second 2x2 piece being mounted on top of that in the corner (see diagram in PDF).  Students can then place the 1x1 either in the holes under the slab or in the regular slots in attempting to balance the assembled structure. Note to teacher: Assembled structure should balance with the 1x1 piece in location shown on diagram in PDF. 5. Students should then experiment with a variety of sizes and shapes, each time attempting to balance some unevenly distributed load.  The crazier the load, the harder it should be to balance, but it will push students to really understand the concept.  It may not be possible to perfectly balance some bizarre shapes or students may find they can only balance it with a 2x1 or a 2x2. URL to PDF file of this activity: http://quantummoxie.wordpress.com/files/2009/10/legoentry.pdf

Lesson Learned: This activity explores the concept of 'center of mass.'  It gives students a hands-on, discovery-based way to understand one of the most fundamental concepts in physics.

Published Monday, December 07, 2009 4:48 PM by dsmith
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