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Re: [RC] Physics - Truman PrevattBruce Weary DC wrote:Kat said:The levers, pullies argument is a total red herring. These devices along with other simple devices, e.g., the screw and gear are used to apply mechanical advantage. The gears on your mountain bike is a good example. The trade off to allow less force to move more force is the distance moved! The work is the SAME. For example you have to peddle many more revolutions in first gear on your mountain bike to move 100 meters than you do in 6th gear. If you did the math you would find the work required to move the bike 100 meters in 1st gear is actually more than in 6th gear since there is loss through friction with every revolution of the peddle. The gears allow force to be applied in a comfortable range (for the rider) to move the bike, e.g. you may not be able to climb a hill in 6th gear you can climb in 1 st gear. HOWEVER, the bike is not adding energy. There is no free lunch supplied by Mother Nature. You do just as much work in 1st gear as you do in 6th gear. The force resulting force - while it might be less is applied over a longer distance. The type one lever may even be more illustrating. In the type one lever the fulcrum (pivot point) is between the load and the point where the force is applied - like a see-saw. The mechanical advantage is given by the ratio between distance applied force and the fulcrum to the distance between the load and the fulcrum. For a mechanical advantage of 2 a 50 pound force can lift a 100 pound weight. However, you have to apply the 50 pound force twice as far since the lever arm is twice as long. If you apply the force for 2 feet, the work is 100 ft pounds and the 100 pound weight is raised by one foot. Again Mother Nature does not supply a free lunch. The energy put into the system is determined by the change in potential energy of the 100 pound weight. The interesting thing is many of the levers in the body are type 3. That is the force applying arm is actually shorter than the arm the force is applied to. For example the human forearm arm. The biceps ties in about one inch or so from the fulcrum (elbow). If you put a 10 pound barbell in your hand the force required by the biceps to perform a curl is much greater than 10 pounds. No matter how you cut it, how good a rider one is, if you post or three point - you double the mass carried you double the work done and you double the energy required to do that work. You can't fool Mother Nature. She is one hell of a lot smarter than any of us. She has been at it since the Big Bang. She knows her stuff. She will extract her fee. These arguments in favor of "weight doesn't matter" fall in the same category as those for the perpetual motion machine. Of course Mother Nature doesn't buy any of it and she is the gate keeper. Truman -- “With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion.” Steven Weinberg – Nobel Laureate, Physics =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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