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[RC] The Physics of Weight - k s swigartBarry Cole said: Bottom line: More weight equals more work as an object is moved. Just Physics, just the facts. Not true. Every other day I have to move a ~100 lb bale of hay from my feed room to my horses' pen, and I have done this in three different ways (depending on the tools I happen to have handy at the time). I have dragged it down the fairly uneven dirt path with a hay hook. The hay hook I am sure, does not weigh more than a pound. I have put it on a two wheel dolly that weighs about 10 pounds but it is kinda old with a kinda loose axle so the solid wheels don't turn all that well and they frequently get stuck on some of the lumps on the path and it requires and extra jerk to get it moving again. And I have put it on a new dolly that weighs about 20 pounds but has smooth running axles and air inflated tires that glides easily over the ground absorbing many of the bumps in the road as if they weren't there. It is MUCH less work for me to move this 100 pound bale of hay with my brand new dolly despite the fact that I have increased the weight of the load by about 10% (which is why I was willing to fork out a rather substantial sum of money to buy it), than with the old dolly (which I got for free from a guy who was leaving town). And it is easier with the old dolly despite the fact that I have increased the weight of the load by about 10%, than if I just drag it across the ground with the hay hook. If adding the weight of a dolly to a load didn't decrease the amount of work that people had to do in order to move an object, there would be no market for them. What I have done is to decrease the coefficient of friction between my load and the surface I am moving it across. Just Physics, just the facts. The coefficient of friction probably doesn't play a big role in attempting to calculate the amount of work that a horse does carrying a load (and so I would probably feel pretty safe in discounting it entirely as a variable if I wanted to create a model of the horse's movement); however, LEVERS, which are another tool that I can use to move more weight with less work, play a HUGE role in how horses carry a load. I believe it was Archimedes who said, "Give me a lever and a place to put it and I can move the world." It is possible to move huge loads with very little work with the proper application of a lever. In fact, horses do this all the time since even my puny little 600 pound horse is a huge load. She holds a substantial portion of that body weight suspended off the ground (i.e. her whole torso) while she is ASLEEP (i.e. not doing any work at all), and she can propel her huge body forward at great speed with very little effort. She has a system of levers and springs and locking and unlocking joints that does a lot of the work for her. So any body who says "More weight equals more work as an object is moved. Just Physics, just the facts." doesn't have a very good understanding of physics. kat Orange County, Calif. p.s. Contrary to Heidi's statement, I am not currently an engineer by trade, although working in an architecture firm exposes me to them on a regular basis. I am, however, an engineer by upbringing, and it is the family trade (and has been for generations). But I didn't need to dust off my old physics text books to remember the principles of physics. I apply them in my daily life when I move a bale of hay. And because I appear to have a better understanding of physics than a lot of people here, I was willing to shell out some cash for a dolly so that I could use the principles of physics to reduce the work associated with moving heavy objects by increasing their weight. Since Home Depot does a brisk business in dollys even to patrons who have never taken a physics class in their lives, you don't have to crack a physics text book to understand the concept. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= 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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