AGBU Vatche & Tamar Manoukian High School’s Mr. Robinson’s Lesson in the Conservation of Momentum

Momentum is a term which can be stated simply as the mass of an object multiplied by the velocity of that object. Momentum is characterized in units of Newtons multiplied by second or in units of kilograms multiplied by meters divided by seconds, however explaining momentum and its conservation in these terms is very dry.

In order to help wrap student minds around momentum, the class had a demonstration last week in order to help make better sense of this complicated idea. Normally, one propels themselves on a skateboard by pressing one foot against the ground. This application of an external force accelerates the rider on the board using friction. How can one propel themselves on a skateboard (on flat land) without using the friction of their shoe?

It turns out that one can propel themselves on a skateboard the same way a rocket ship propels itself into space, though the results may not be as spectacular. If you fire a fuel source (or a 10 pound red ball) in one direction, the conservation of the momentum will propel you in the opposite direction. Click here and find the numerical solution to the situation presented in the video.

A.G.B.U. Vatche & Tamar Manoukian High School, 2495 East Mountain St., Pasadena, (626) 794-0363 or visit



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