What is the reason why hubcaps on cars appear to go backwards when they reach a certain speed?
458532
This effect is called aliasing.  It happens whenever the sample rate falls below twice the rate of rotation of the tires.  Imagine a tire with a marker on the top (at rest) and start spinning it 1 time a second. Also imagine you are taking pictures of it every 3/4 of a second.  The first picture, the mark will appear at the 3/4 position around.  The second picture, the mark will apear at the 1/2 position, then the 1/4, and so on.  When you play them back, the tire will appear to spinning backwards.
52429
One of the classic inefficiencies of cars of yore is the driveline design.  Take for instance a 1962 V-8 Impala with a hydramatic transmission and rear wheel drive.  The two-speed transmission always allowed slippage between the engine and the wheels, which caused energy loss in the transmission fluid being heated up in the torque converter during all driving situations.  They have cured that in today's automobiles by locking out the torque converter with an automatic clutch.  Putting a 90 degree angle between the input and output is also an energy sucker.  In more efficient front wheel drive cars, the axis of engine revolution is the same as the wheels.  This saves some energy as well. The final drive ratios of cars in the 60's was insane!  A cruising RPM of 3600 at highway speeds was not unheard of--and on a V8!!! Think of the gas going down the tubes.....  Modern cars reduce the final drive ratio and add overdrive to the transmission to reduce cruising speed RPM.  Less RPM means less air consumption and less fuel use.  In the 70's, they caught on and offered rear wheel drive cars with 2.73:1 rear end ratios to save gas.  This hurt acceleration, but was cheaper than offering a 4 speed automatic.  (It eventually happened.)  \n\nA huge determinant of efficiency is COMPRESSION RATIO.  Without computer control and injection, most cars of the 70's (BAD efficiency) had LOW compression ratios, say 8.0.  (And food for thought--the first spark ignition engines had a sorry compression ratio of 4.0:1.  How sad!!  They did not know enough about fuel chemistry at the turn of the century, so that's why the horsepower value of vehicles was so low back in the teens. A four cylinder automotive engine having 10hp in the "old days" with a displacement of 2 liters.  WOW!) New cars have all kinds of tricks to increase compression ratios while running on regular 87 octane fuel.  Current compression ratios include 9.0 to 10.1.  Computers adjust injection and spark ignition timing (to repeat a collegue's information already submitted) along with monitoring piezoelectrick "knock" sensors which make adjustments for preignition "pinging."  In the old carbureted cars, even ones with HEI ignition, there was no way to deal with the pinging. The sure fire way to prevent pinging (and serious damage) is to lower the compression ratio.\n\nAnother huge problem with cars of the 70's and 80's were the addition of the catalytic converter and other emission control systems like the huge drain from a "smog pump."  EGR valves put exhaust in the intake charge to reduce nitrous oxides, but that reduces peak combustion temperatures and the available power from the fuel charge.  Running exhaust through the manifold also made the intake charge hotter, reducing efficiency.  Old cars had fixed valve timing, which determines the relationship between power at high rpm and torque at low rpm.  Some manufactures today have adjustment on the exhaust valve timing, and some even adjust both the exhaust and the intake timing to increase efficiency and torque at low RPM while changing valve overlap for high rpm horsepower with a net smaller displacement.\n\nSome modern cars still include EGR, but the catalytic converter technology is much better and more attention to exhaust system design has helped increase MPG.\n\nThe actual energy used by the valvetrain has also been reduced by reducing the mass of the components in the valve train.  Using a cog belt to a cam riding right above the valves reduces the energy used to activate the valves.  That can really add up over the life of the engine.  \n\nAnother development was the inclusion of the electric cooling fan.  Belt driven fans consumed huge amounts of power from the engine, even if they had a thermal clutch.  Flex fans were supposed to reduce energy, but we are still talkin' in the multi-horsepower range just to move air across the radiator.  The modern c
740143
it may be that the speed is so fast that it may have reached the maximum speed.... this could be the maximum limit..\nit's critical by common sense...\ncheck the dictionary, or thesaurus....
82342
This is an impossibility.  Cars don't travel at the speed of light.
163803
when the windows are rolled up the air in the car isn't moving as fast as the air outside the car. the air is moving as it would if the car were perfectly still almost
490009
Because the normal force of the road upon the car is not directed straight upwards, as it is on a flat road. The normal force vector is tilted inward toward the center of the radius of curvature (assuming that the road engineers built the darned thing correctly) by an amount equal to the angle of the bank of the road. Decomposing the normal force vector into a horizontal (towards the center of the circle) and a vertical (up towards the sky) shows an increased force upon the car towards the center of the radius of curvature over the case where the road is flat. In the end, it means that the coefficient of static friction that keeps the wheels from sliding radially away from the center of curvature doesn't need to be as high when the road is banked.\n\nAlso note: There is NO SUCH THING AS CENTRIFUGAL FORCE! The car is an accelerating reference frame. Anyone who uses the term "centrifugal force" either has not taken 1st year physics or did not understand it when they did.
79821
Simple answer is NOTHING.  This is the explaination:  When you are traveling in a car at 70 MPH and there is a bug flying around in the car (say 0.5MPH), the bug is also traveling at 70 MPH ().5MPH can be ignored as bug is flying around in the car with null effect on the speed).  This is the part of theory of relativity.  Now let's see our car is traveling at the sped of light, when you turn the light on, the rays are traveling at the same spped and you see no effect of light (i.e. still dark-if driving at night).  If you just slow down at little (say 5%) then you will see light just ahead of the car and same applies as if you spped up the car slightly, it will be still dar and you may see back of the car lit (light left behind) for having lheadights in the front.
704494
Have people never seen a real helicopter close by.... of course the rotors appear to go backwards... It is an optical illusion but it is exactly the same as a spinning bike wheel. When it reaches a certain speed the eye See's a part of it slow down and then it appear to go slowly backwards...... until it's just a blur again....\n\nI will go look for what the term for this is called and will be back with an edit shortly ;o)\n\nOK Back. I found this....\nImagine a clock with just a minute hand. If we were to look at the clock every 59 minutes it will appear to have gone backwards by one minute each time and if we look every sixty minutes it will appear not to have moved at all! So to accurately observe the minute hand in motion we must look at the clock more frequently than every sixty minutes, in fact we must look at it every thirty minutes. This is known as Nyquist's theorem.\n\nGraham
844700
Mostly for easy acces in and out of the car, also the wheel is marked showing the center of the wheel to the steering colum.  If something should knock out the alinment the driver can compensate by removing the wheel and turn it left or right so the steering is center again.
150717
The ones I have seen are vertical walls in the shape of a cylinder. like a soup can.  A car or motorcycle, or bicycle enters into it and when they are going fast enuf they can travel up the walls.  The car or bike has to be going very fast.  If they slow down they will fall off the wall, and thats why its a wall of "Death"
413558
Yes,but it's providing downforce to stick car to track better.The car is going to cut the air,and you sure don't want it to go under,then car would lift up and get airborn.
955526
Light moves slower through denser media because more particles get in its way. Each time the light bumps into a particle of the medium, the light gets absorbed which causes the particle to vibrate a little and then the light gets re-emitted. This process causes a time delay in the light's movement so the more particles there are (the more dense the medium), then the more the light will be slowed down.\n\nAs the light 'slows' down, it will then bends towards the normal.\n\nthink of a car with 4 wheels getting into a sand area from the road. as the one of the two front wheels hit the sand, it encounters resistance n hence slows down. however, the other three wheels are still moving at the normal speed. this results in the whole car moving forward but turned in the direction of the first wheel that was slowed down by the sand.
176123
The force that pulls you towards the side of your car when you go around a corner too fast is actually inertia.  It's the same force that makes you fly forward when you hit the brakes too fast or sink into your seat when you lay on the gas.  According to Newton (I believe it's his third law), "an object in motion tends to stay in motion and an object at rest tends to stay at rest."  Well when you are in your car and you are moving in a straight line, your tendency is to keep moving in that straight line.  When you take the turn too sharply, the car is turning but your body's natural tendency is to keep moving in that straight line, so you get pushed up against the side of the car.  The same justification explains why you move forward or back when the car accelerates or decelerates too quickly.\n\nCoriolis force is a completely different force that is caused by the rotation of a sphere and the fact that the sphere is densest in the middle, with decreasing density as you approach the poles.  This change in density causes a force which makes moving things tend to move towards the equator of the sphere.
1165249
This is the part of the wikipedia that I understood.  I can explain it to you if you want to send me a message.  I think it makes alot of sense.\nNow let’s see what happens to our accelerating particles when a torque is applied to the spinning wheel. Assume the axis of rotation created by the torque is through the center of the wheel at 90 degrees to the primary rotation of the wheel. Let’s look at a particle that is on this axis of rotation. Since the particle is on the axis of rotation there is no direct motion applied to the particle at the instant of the applied torque. But let’s look at what will need to happen at the next moment in time. The particle is now going to be forced to curve again. This time in the direction of the curve so as to accommodate the tilt of the wheel. Now we have a particle that is already moving and it wants to keep moving in a straight line. So the particle will exert a force on the wheel. If you look at a particle on the other side of the wheel you will see that the force of the second particle is in the opposite direction of the first particle. That pair of unmatched forced is what causes the precession torque that is 90 degrees to the applied torque
302547
When a vehicle accelerates forward, there is inertia that holds us back until we compensate for it.  The air in the bus also moves forward because it is contained and restrained by the walls, roof, floor, and windows.  The air that the bug is flying in is also first compressed in a backward motion and then stabilized.  Its a good thing, else when the bus moved forward if all the air pooled on the back window then the driver and everyone up front couldn't breathe.  Just as that air exerts an outward pressure upon itself and everything else (if there were no pressure, there would be no wind resistance) that keeps it from collapsing at the back of the bus when it moves forward, the bug continues flying by the same aerodynamics that permits it to fly in the first place.
89490
check your wheels,... are they properly aligned? Also go for computerised wheel balancing.\nAnd better be careful. Don't drive too fast till you get the prob rectified. If you brake suddenly then the car might skid or turn around.
426870
I picture an axle with one wheel bigger than the other for this problem. Since they're not spinning, wheel A has to cover the same amount of distance wheel B covers in the same amount of time.\n\nWheel A has radius 12cm and rotates at 35 radians/second:\n12 cm * 35 rad/sec = 420 cm / sec.\n\nWheel B must also cover 420 cm each second. So we work backwards:\n\n(420 cm / sec) / 17 cm = 24.7 rad / sec\n\nSo you're right, B is the correct answer.