Chas
Well-Known Member
An old advert produced by Hyundai a few years ago
https://www.facebook.com/video.php?v=10152706823933403
https://www.facebook.com/video.php?v=10152706823933403
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Can a car go faster than an arrow?
- Thread starter Chas
- Start date
Clever bit of filming though.
So if the archer had been standing on the roof of the car facing backwards, the arrow he shot would have been stationary, relative to the earth and it would have just dropped straight to the ground.
So if the archer had been standing on the roof of the car facing backwards, the arrow he shot would have been stationary, relative to the earth and it would have just dropped straight to the ground.
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The car had a head start whereas the arrow was doing 0mph when the car passed it. Clever theme though.
Chas
Well-Known Member
But an arrow does 0-max speed as soon as the string is released whereas the car needs time to get up speed so it is a fair start.
Chas
Well-Known Member
Clever bit of filming though.
So if the archer had been standing on the roof of the car facing backwards, the arrow he shot would have been stationary, relative to the earth and it would have just dropped straight to the ground.
I think it would still have flown backwards, the energy stored in the string would be transferred to the arrow so forcing it away from the bow.
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But the bow would have been traveling backwards at the speed of the car, so yes, it would have left the bow OK, but the arrow would, in theory, have been stationary relative to the ground.
Towpack
Well-Known Member
Clever bit of filming though.
So if the archer had been standing on the roof of the car facing backwards, the arrow he shot would have been stationary, relative to the earth and it would have just dropped straight to the ground.
In theory yes but I reckon wind resistance will play a part. The arrow wouldn't have to overcome any, in fact it will have , say, a 60mph wind helping it initially so would almost certainly fly a short distance. JMO
Chas
Well-Known Member
I reckon it will fly the same distance as if it was shot from a stationary position, relative to the bow though it would fly even further.
Towpack
Well-Known Member
I'm not so sure. You have to subtract the forward speed of the car from the rearward speed of the arrow. The string of the bow accelerates towards the bow itself but the bow is moving towards the string at whatever speed the car is travelling. So if both speeds are 60mph then the arrow is effectively stationary relative to earth, the only other influencing factor being the wind/airflow. If you do this in a vacuum the arrow would probably fall straight to earth.
Chas, I believe you have an LC with a roof rack and your also into archery. Time for an experiment me thinks! Feel free to post up the video!
Ha ha 
Chas
Well-Known Member
The force the string applies to the arrow is the same whatever direction the bow is travelling so therefore the arrow will fly.
My rack has the roof tent remember so nowhere to grip onto, sorry but no pictures.
Do you think I'm that stupid?
. . . . Don't answer that.
My rack has the roof tent remember so nowhere to grip onto, sorry but no pictures.
Do you think I'm that stupid?
Towpack
Well-Known Member
Let's ignore the effect of the wind on the arrow for a moment. All speed measurements are relative to a particular point, wether it's moving or stationary. The arrow will 'fly' relative to the bow and the car, but assuming the forward speed of the car and the speed the arrow leaves the bow are the same, the arrow will not be moving relative to the ground. If you fire the arrow forwards from the moving car the arrow will be travelling at 120mph relative to the ground and 60mph relative to the car. Fire the arrow when the car stops and the arrows speed is 60mph. This applies to anything, arrows, bullitts, even throwing a ball etc, except the speed of light, cue Einsteins theory.
Chas
Well-Known Member
On a car travelling at the speed of light will headlights still shine forward?
Towpack
Well-Known Member
Apparently not according to the theory. The speed of light is both absolute and constant meaning nothing can go faster, even light itself. If you measure the speed of the light coming from the rotating Sun the light from the edge rotating towards the earth should be travelling faster than the light from the receding edge but it isn't, it's the same. This has been done but don't ask me how!
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So if a forward facing torch were travelling at the speed of light and you turned it on would any light come out of it? Does it depend on the relative speed of the observer?
From what I remember from all the quantum physics I learned at A level (i.e. None) wouldn't the torch turn into a banana or something after exceeding the speed of light?
Where's Einstein when you need him?
Coming back to my more earthly example and theory, if the car had been going at twice the speed say 400 kph the same arrow fired at 200 kph would have been travelling backwards (relative to the ground) at -200 kph. (Ignoring annoying factors like wind resistance and arrows not flying backwards very efficiently.... )
BTW, I've just watched it again and it was a beautiful shot. Such a lot of elevation needed and dead centre target too, and perfectly on camera cue. Nice
Where's Einstein when you need him?
Coming back to my more earthly example and theory, if the car had been going at twice the speed say 400 kph the same arrow fired at 200 kph would have been travelling backwards (relative to the ground) at -200 kph. (Ignoring annoying factors like wind resistance and arrows not flying backwards very efficiently.... )
BTW, I've just watched it again and it was a beautiful shot. Such a lot of elevation needed and dead centre target too, and perfectly on camera cue. Nice
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Holding on to the roof of a car while it accelerates to 100mph is easy ..... but you don't want to be there when it starts decelerating .... and you won't be if the driver touches the brakes . Lancia Delta on the Ballamodha straight many years ago and even the memory still hurts 
Towpack
Well-Known Member
If you were also travelling at the speed of light then you would see the light from the torch but this would mean that for anyone who was stood still, the light from the torch would be travelling at twice the speed of light which is impossible. This is why, according to Einstein, that for this to happen, as you approach the speed of light time would slow down, your mass would increase and the length of the vehicle you are travelling in would shorten. When you reach the speed of light, time would stop and your mass would become infinite which is why it is impossible for anyone/anything to travel at light speed. Can we get back to Landcruisers now please!
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