Nick writes: > There is a difference between the force applied and the amount of > energy required to generate that force. Effort and force aren't > really the same thing. Any propulsion force will create an > acceleration in the direction of the force. (F=ma). True. You're defining "propulsion force" as "that component of applied force that goes in to producing forward propulsion", right? > ...However, you may end up applying > more energy into creating the force than you receive out of it. Right. Some of your energy will go into just heating the water. >...So > even though the force applied to the paddle exactly equals the force > applied to the boat, Right, Newton's third law. >... you can not say that the energy applied to the > paddle is equal to the energy received by the boat. Absolutely. > Energy received by the boat is equal to the energy applied to the > paddle minus the energy received by the water. Efficiency is (Energy > to Kayak)/(Energy to Paddle) and not (Force to Kayak/Force to Paddle). We agree completely. I think most of the disagreement was indeed due to our not all agreeing on the meaning of the terms we were using. -- mike --------------------------------------------------------------- Michael Edelman mje_at_spamcop.net http://www.foldingkayaks.org (nomadics) http://www.findascope.com (choosing a telescope) *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
"Peter A. Chopelas" <pac_at_premier1.net> wrote: > That is what I meant when I said the high aspect ratio paddle is more > efficient for sea kayaking than the low aspect ratio "Euro" paddles. > The high aspect ratio paddle will use less power (fewer calories) > traveling the same distance at the same speed. And that is a fact of > fluid mechanics, not a theory or an opinion. I would agree that biomechanically, a high aspect ratio paddle is more efficient for paddling long distances. It is not a fact of fluid mechanics though--once you're talking about calorie usage and human efficiency, you have ceased to discuss pure fluid mechanics. You're not using less power due to the paddle-water interface, but due to the limits of the human end of the system. Shawn Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/ *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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