im scratching my head now. When you watch the wheels of a car going around they appear to be going one direction. As you continue to watch they appear to slow down, stop and then go back the other direction. Obviously the vehicle is still going in the same direction, so why does the eye play this trick on you????????????????????????????
ok scientists and ologists explain this one to me then
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its to do with how fast your eye sees and the speed the wheel is going around at.
a similar / even dangerous thing can occur in workshops
a lathe for example if its chuck gets to the right speed ( i am guessing its 3000 rpm), if it is lit by flourescent lights it can appear to be standing still.
why
because the light flickers at 50hz (50 times/second) the chuck appears to stay still as it's speed is relative to 50hz
a similar / even dangerous thing can occur in workshops
a lathe for example if its chuck gets to the right speed ( i am guessing its 3000 rpm), if it is lit by flourescent lights it can appear to be standing still.
why
because the light flickers at 50hz (50 times/second) the chuck appears to stay still as it's speed is relative to 50hz
It's all to do with how fast the human eye can take in information (could be wrong,but I think it's 16 "frames" per second)
When a wheel is rotating slowly,the eye can see it all
When it speeds up,the eye struggles to match the speed,until it gets to a point where the spokes on a wheel are moving that fast that the eye cannot keep up,and the last image stored on the retina has the spokes slightly ahead (in a rotational way) of the next image,so they appear to be going backwards.
The "slowing down" is the speed of rotation falling into line with the speed of the eye - when the two are perfectly synchronised,the wheel appears to be still.
Same principle as strobosynchroscopes on record decks (for those who remeber life before the compact disc
)
When a wheel is rotating slowly,the eye can see it all
When it speeds up,the eye struggles to match the speed,until it gets to a point where the spokes on a wheel are moving that fast that the eye cannot keep up,and the last image stored on the retina has the spokes slightly ahead (in a rotational way) of the next image,so they appear to be going backwards.
The "slowing down" is the speed of rotation falling into line with the speed of the eye - when the two are perfectly synchronised,the wheel appears to be still.
Same principle as strobosynchroscopes on record decks (for those who remeber life before the compact disc
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It is called the stroboscopic effect, and can be reduced in three phase installs by operating lights across all three phases.
Do a Google on it and see.
Do a Google on it and see.
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I know this will sound strange, but when you get that effect, (and it is not dangerous to do it), try blinking your eyes very fast continuously; you can get an even stranger effect when in a dance club and the strobe lights come into play, it will all appear as an old style, unsynchronized film.
There, back to my box!
There, back to my box!
Just keep your fingers crossed that the wind don't change when your doing it !!! (blinking your eyes that is).
what about the 'Moire pattern' formed by your eye when two sets of lines or other regular patterns overlap.well its interesting.
what about the 'Moire pattern' formed by your eye when two sets of lines or other regular patterns overlap.well its interesting.
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Is that the visual effect you get where a craftily drawn black and white sketch makes you dizzy and feel queasy?
All very well, but going back to the original question, when a wheel is in contact with the ground the bit on the road is actually stationary. If it was going forwards then the wheel would be skidding. Similarly the part of the tyre about to touch the road is going backwards relative to the car and is decelerating towards zero mph relative to the road. Following the point of contact the speed of the tyre accelerates relative to the car, overtakes it at the top of its revolution and so on.
And it all appears so easy!!
I'd never really thought about it before but I seem to remember having some bl**dy awkward applied maths question about this in my youth (long gone).
And it all appears so easy!!
I'd never really thought about it before but I seem to remember having some bl**dy awkward applied maths question about this in my youth (long gone).
get your head around this then, as a tank moves forward at say 60 mph, the bottom of the track is in contact with the road and therefore stationary. Does that mean that the top part of the track is going at 60 or even faster to maintain the speed?
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