why does a tyre appear to spin backwards at a certain speed?
149524
Think of how animation works.  You see a picture, then a short time later, you see a slightly different one.  If the time between pictures is short enough, your brain interprets this as a moving picture.  (Why your brain does this has traditionally been attributed to the phenomenon of "persistence of vision", but it is likely much more complicated than that."  )  \n\nNow imagine a tire (sorry, I'm American, so I'll stick to our spelling) that has a white letter M (for Michelin) on it's sidewall.  The tire is spinning, so the letter M moves in a cirle, so that you see the white M at the top of the circle, then a short time later see it at the top of the circle, then a short time later at the top of the circle again, etc.  Because of the way the brain processes information, at a certain speed the brain will interpret this successive sightings of the M at the top of the circle as the M remaining stationary.  \n\nNow imagine the tire spinning a little slower, so that the M doesn't quite make it all the way around the circle before it is perceived again. The M started at the top of the circle, then the next time it was perceived it was located at say 11 o'clock, then the next time at  10 o'clock, etc.  Now, your brain will interpret the succesive pictures of the M as the M moving backwards.\n\nThis effect is even more pronounced in movies and TV, where the technology forces us to see motion split up into successive frames.  It is also the principle behind the timing light used to tune auto engines, for example.  A light that strobes on and off at a set frequency allows the mechanic to determine how fast the engine is turning by observing the motion, and adjusting the frequency so that the engine appears to be motionless.
649589
it's to emulate the effect of cycling on a real bike. IF there was no weight to cycle against, your legs could spin round and round very fast with no resistance. Cycling against the flywheel, it's tough to start it spinning and get up to speed, like on a real bike, and to keep it going round at speed takes effort, like a real bike.
1177357
Friction, it's the same reason your tires make that sound if you try to come to a stop too quickly.
641452
opposite force being applied
211260
If I ever used the front brakes, it would be after I spun around and was going backwards. \n\nOtherwise a T stop is what you use if staying forward.  (bring 1 leg behind and perpendicular to stop.)  I still prefer the turn around method though, less noise.
932837
forces are opposite and equal, otherwise you would change speed/direction.
553294
The car's wheels have lost all the rubber on the tires, and\nit is riding, literally on its rims(or wheels).  Is this a test?
234240
Because if it went counterclockwise time would be going in reverse? :)
845422
This is related to Newton's law: An object in motion or at rest will stay in motion or at rest unless acted upon by an external force.\n\nTo elaborate, an object travelling in a straight line will keep on travelling in that straight line at a constant speed unless something acts on it.\n\nWhen you are in the car with your ball, everything in the car is travelling at the same speed, so you through the ball up and it comes straight back down. But if you throw the ball up and then jam on the cars brakes, the ball will keep moving at its original speed but the car is slowing down, so the ball would fly forward into the front windshield.\n\nLast point, if you throw the ball out the window, it will appear to fly backwards - It is just slowing down compared to the car because unlike the air inside the car, the air outside is at rest, so the ball will be flying through the air at a high speed and the wind drag will slow it quite rapidly.
914874
yes if it is spinning on its own axis as it moves.  This is called Spin Angular Momentum
228872
Centrifugal force will pull away from center tyre walls making them more tense and making contrary effects of air pressure...
519407
they're called Rollie Reds or something...basically its magnets...there's mini brakes on the wheels so instead of rolling it just stops!
623548
This happens with fan blades and rims on car tires.\n\nYour eye can only process information so quickly.\nWhen this happens the wheel is turning faster than your eye and brain can process.  So you expect the single point on the wheel to advance to a certain space but it moved so far the next momment your brain can process the information it looks like it is behind where you last saw it.  Therefor it looks like it moved backwards.  This is easier to explain with pictures.  I hope this helps.
858812
Not sure about a website but the physics would be similar to what causes corrugations in a dirt road.  The vibration frequency would be related to the speed of the wheels.
1039588
Nothing to do with angular momentum. \n\nIf you weight the rims of the wheels of a bike to increase the angular momentum so that the wheels behave like a gyroscope (bike wheels are really light usually), the bike becomes almost impossible to ride.\n\nA bike stays upright because the centre of gravity at the front wheel is slightly behind where the wheel touches the ground (the bike forks bend forward). Because of this, if the bike tips to the right the front wheel turns to the left and vice versa. \n\nIf the bike is stationary this does not help a lot.\n\nBut if it is moving forward this tends to steer the bike out of toppling in the direction of lean, and this helps you to balance the bike ( a bike with no rider always falls over - its your sense of balance that keeps it upright).\n\nThe fast the bike goes, the more pronounced the self correcting steering is.\n\nPS bikes have been made with the forks bent backwards so that the self steering is in the direction of lean, so exaggerating a loss of balance -it is hysterical to see someone try to ride this sort of bike
1136402
The power transmission system in a bi-cycle is of chain type. The mechanism is as follows. The larger driving sprocket is driven by the motion of pedals. The roller-bush type chain connecting the driving sprocket and the smaller driven sprocket transmits power from pedal to the rear wheel. Due to the smaller size of the driven sprocket, the speed multiplication occurs ( the speed of rotation of rear wheel is larger than speed of rotating the paddle).\n\n[You may also note: A chain, like a power transmission belt, has a taut and a slack side. In usual conditions i.e. while going forward, the slack side is at the bottom and taut side at the top. If the direction of rotation of pedal is reversed, the top side of the chain becomes slack and bottom side is taut.]\n\nLet us come to the specific topic now.  While doing reverse paddle, the chain tends to drive the driven sprocket in opposite direction. The smaller sprocket is provided with "ratchet-shaped" teeth. So the chain and driven sprocket doesn't mesh but slips. Thus preventing any power transmission to the rear wheel. Thus there is no motion of rear wheel and hence the cycle cannot be driven backwards.\n\nLearn about ratchet from
147563
Look at how a bug does it.\nThe side opposite the direction you wish to turn takes steps slightly longer than the side toward the turn.\nFor very quick turning, the legs take strides in opposite directions.