# Science 101: Why Don't All Rolling Objects Reach the Bottom of an Incline at the Same Time?by: Bill Robertson

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This column provides background science information for elementary teachers. In this month’s issue the author discusses motion and friction.

• Elementary
10/1/2011

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Reviews (3)
• on Wed Nov 16, 2011 11:21 AM

If you have ever wondered about rolling objects, especially ones that roll down inclines, then you are in for a treat. This article is filled with fun things to do and much to learn about as motion and friction interact in the real world. The fact is that not all matter responds the same and it is the distribution of matter that can throw you off your game. This is a good article from this well know author that helps you understand matter and friction and gravity.

Adah (San Antonio, TX)

• on Sun Oct 16, 2011 6:40 PM

Very well written, especially if you are needing some extra background to help you teach the concepts of motion, friction, and gravity. The author (famous for his series "Stop Faking It!") uses humor in his delivery of examples and activities to help the teacher/student understand the principles being used and demonstrated. Although written for upper elementary, I feel that middle school teachers would benefit from reading and using some of the included activities mentioned.

Sue Garcia

• on Thu Aug 23, 2012 1:07 AM

Almost everyone is familiar with inertia and that objects resist changes to motion, but I think the idea of 'moment of inertia' eludes many. This is unfortunate, because many important objects in our life spin, and you can't understand spinning motion without understanding the moment of inertia. The full story of what a moment of inertia is and how to assign one to an object is worth exploring for those who wish to go deeper. It would also be worthwhile to find some objects of differing mass to roll that result in a tie. In any case, I encourage any one who lacks insight into the nature of spinning motion to start with this article.

Eric Carlson (Royal City, WA)