Hi John ; John Mullan <[EMAIL PROTECTED]> wrote: > Cool. This is the first time I've heard these > things explained this way. > > Can I ask: Just what is the equivilent description > of centrifugal force? > Does it apply to me spinning a pail of water such > that the water doesn't > fall out? > > Just satifying my thirst for knowledge :-) >
Ask away. No problem. I usually ponder things like this until they make sense. Makes some people crazy. Hmm. Let's see. Let's say you contruct a metal frame with a bucket of water hanging like a swing in the center. The bucket is free to swing any way it wants to. Now we mount this frame and swinging bucket of water on a rocket sled. If we accelerate the rocket sled at g (9.8m/sec2), the bucket will swing towards the back of the sled at a 45 degree angle. If we do it smoothly, no water will spill out. Other rates of acceleration will produce other angles of swing, higher acceleration will swing more, lower accelertations will swing less. The amount of swing would be proportional to the ratio of sled acceleration to g. If we really accelerate the sled at a very high rate, the bucket will swing out almost to a horizontal position and no water will spill. No one would call this centrifugal force, right? But the bucket wants to remain stationary, and so resists the acceleration caused by the rocket sled. No one would call this centifugal force. Now if we swing the bucket around us in a circle and we accelerate the bucket at a rate of g (same 9.8m/sec2), the same thing will happen, ie. the bucket will swing out at a 45 degree angle and no water will spill. The string is putting a force on the bucket towards the center of the circle in the same way as the rocket sled was putting a force on the bucket towards the front of the sled The bucket in turn is putting a force on the water, exactly as in the rocket sled example. The only difference is that the force of circular acceleration is at RIGHT ANGLES to the direction of motion. The bucket wants to continue in a straight line, and the string is putting a force on the bucket at right angle to its direction. This results in changing direction rather than changing speed. The force of acceleration in the rocket sled example is ALONG (parallel to) the direction of motion. This results in changing speed rather than changing direction. However, both are accelerations. If there was such a thing as centrifugal force, it would also describe the rocket sled example. There is no such thing. Hope we haven't gotten too far off topic. Best Regards, Peter G. Thailand > John > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] > Behalf Of Guag Meister > Sent: October 26, 2004 1:19 AM > To: [EMAIL PROTECTED] > Subject: Re: [Biofuel] Canadian Trash > > > Hi Eric ; > > Eric wrote : > > I really don't understand this assertion. (And I > saw > > it on the web pages from scientists as well.) > Saying > > that the force is an illusion. If you put a spring > > between my hand and the ball it would compress. A > > spring needs a force pushing it from both ends to > do > > that. No exceptions. > > This is a good question. I guess that the word > illusion is maybe not a good choice, in that you > feel > it. But your hand is supplying the force to the > ball. > not the other way around. Your hand by itself > couldn't do it anyway. Your hand is connected to > your > body which is connected to your feet which are > hopefully stationary on the ground due to friction > of > your shoes. When you push the ball, the force you > are > suppling to the ball is transmitted in the opposite > direction to your feet and ultimately to the earth. > The earth will move slightly in the opposaite > direction (like 1e-20 meters, depending on the > acceleration of the ball). > > I have yet another way to describe this. Let's say > you are standing on the earth and you fire a bullet > horizontally. What happens? The bullet wants to go > straight, but it is acted on by gravity. So it > begins > to fall toward the surface of the earth while moving > at high speed horizontally. Now the surface of the > earth is curved, so as the bullet moves horizontally > a > lot and falls a liittle, the surface of the earth is > "falling away" from the bullet due to the surface > curvature. There is NEVER any centrifugal force. > What is happening for an object in orbit is that the > object is "falling" towards the earth exactly as > fast > as the surface of the earth is "falling" away. The > object moves horizontally and falls a little. The > surface of the earth has fallen a little. When > these > two rates are exactly equal, the object is in orbit. > > If someone went up to 100 miles and dropped a stone. > It would fall straight down due to gravity. If you > threw it horizontally at 100 mph it would fall in a > curved path and land a few hundred miles from you. > If > you threw it at 1,000 mph it would land much further > from you. If you threw it at 16,500 mph it would > almost make it around the earth before landing. If > you threw it at exactly the right speed > (approximately > 17,500 mph for near earth orbit), it would be > falling > at exactly the same rate as the surface of the earth > is "Falling". If will never land, ie. it is in > orbit.. There is NEVER any centrifugal force. Only > centripital force of gravity, directed toward the > center of the earth, which is causing the curved > path. > > If you threw it faster than 17,500 mph, say 18,500 > mph, the centripital force of gravity would not be > enough to curve the objects path fast enough to stay > along the curvature of the earth, and the object > would > move further into space. This is NOT centrifugal > force. It is insufficient centripital force. > > Autronauts in orbit are weightless because they are > continuously "Falling" (ie. accellerating towards > the > earth due to gravity). They feel just as you would > feel if you were in an elevator and someone cut the > rope. When you accelerate at g towards the earth > you > become weightless. The astronauts are "falling" ALL > THE TIME. They just happen to be moving > horizontally > fast enough so that the surface of the earth curves > away from them so the never hit it. > > Whew! Hope this helps. > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail Address AutoComplete - You start. We > finish. > http://promotions.yahoo.com/new_mail > _______________________________________________ > Biofuel mailing list > [EMAIL PROTECTED] > http://wwia.org/mailman/listinfo.cgi/biofuel > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Biofuel archives at Infoarchive.net (searchable): > http://infoarchive.net/sgroup/biofuel/ > > _______________________________________________ > Biofuel mailing list > [EMAIL PROTECTED] > http://wwia.org/mailman/listinfo.cgi/biofuel > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Biofuel archives at Infoarchive.net (searchable): > http://infoarchive.net/sgroup/biofuel/ > __________________________________ Do you Yahoo!? Yahoo! Mail Address AutoComplete - You start. 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