Measuring Irregular Body Center of Mass
Date: Summer 2013
Hi. The water rocket is made out of a 1.23 L soda bottle, the height of the rocket is 45 cm with the nose cone. How do i measure 'centre of the mass' of the bottle rocket?
The easiest way is to balance the bottle when filled and ready to go, over the edge of a yardstick, if filled to capacity. If partially filled, choose to ignore the weight of nose cone and the opening end, note the height of the water and divide by 2.
One thing to keep in mind that is crucial - the center of mass will be changing as the water exits! So the key is to make the drag of the fins sufficient to force the nose forward.
Thanks, Peter E. Hughes, Ph.D. Milford, NH
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Update: November 2011