If you're travelling in a car in the speed of light, What will happen if you sounded the horn?

the horn will have to catch up to you, you wouldn't see him coming because he's traveling as fast as any light off his car.

the horn would be on a noticeable delay, cus the speed of light is so much faster than the speed of sound. u would crash before the horn sounds

There will be NO HORN left at that speed...everithing would be dissintegrated....and sounding a horn...to who or what?
sound would be left thousandths of kilometers behind (some few millions).......IF there was still a horn

well the whole light-speed-car scenario is just a TEENY bit outlandish, i would guess sounding the horn would cause a near instantaneous sonic boom as the speed of light is way faster than the speed of sound. but i would guess the 1 quintillion quadrillion gazillion Gs exerted on you in a light-speed car would be a more pressing concern."sonic BOOM!" - Guile from Street Fighter

well the horn wouldn't be heard until after the other car pass you. and if you can "see" the other car coming at you, unless you are playing light speed chicken, then all you would have to do is change lanes or trajectory to avoid the collision.

You will hear the horn fine because it is traveling the same speed as you.  It's usefulness is another issue.

energy horn sounding is lost in midst of collision & fireball,,,,,,a hypothetical survivor hears horn (produced before collision) after fireball and other energy of kaboom have dissipated

we know that speed of light is faster than of the sound... and according to the theory of relativity of einstine, the hearer cannot hear the sound...

sorry to inform u but at the speed of light your car or what ever you are in would go from the point you reached the speed of light to the point you left the speed of light (time dilation). so at the speed of light time does not exist from your perspective, even tho in one years time for everyone else you would travel a light year... and no time would pass for you(i don't think i can stress this enough every one keeps forgetting about that side effect)

The two cars are gonna be pulverized into a haze of atoms very shortly. There's no way for either to warn the other. Sound from your horn can't reach the other car in time because your combined closing speed is much faster than that of sound. Think about lightning and thunder and why you see the lightning before you hear the thunder.

If both cars were heading towards each other faster than light speed neither would see the other at all because the physical cars are outrunning their light.

Now if you want to get real technical about both cars moving faster than light the situation would be that both cars would have infinite mass (..all the mass in the universe..) and it would have taken infinite energy (..all the energy in the universe..) to get them up to their velocities. But then we're left with the question of where are we going to come up with any energy to put into the collision since there's none left in the entire universe. Spooky huh...?

At sea level, sound travels at approx. 340 m/sec through the air.   It travels approx. 1500 m/sec through salt water. But, does sound travel through a vacuum such as in outer space?   At any level, light travels at 299,792,458 m/sec. If  you are approaching the speed of light in outer space you would be going so much faster than the speed of sound (provided sound travels through a vacuum) that you would have traveled approx. 299,792,458 meters after the first second, while the sound could have traveled only a maximum of 1500 meters after the first second if the medium were salt water. But you raise an interesting question concerning speed. If you are both approaching at near the speed of light, you are approaching at speed of light x 2.  Would that be possible?  There would be a cosmic collision at those speeds.  At a more mundane level, fighter pilots can overshoot the missiles they fire and become the missile's target because they are traveling faster than the missile when it is first fired. The same idea applies to your scenario. You would overshoot the sound waves.

u will have an accident before the other hears ur horn.
to prevent accidevt swerve quickly