101 Reply by avogadro (edited by avogadro 09-Mar-2009 14:06:04)

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Re: Anser me this

i thought of that too, but as you already stated it wouldnt work, and you're giving too much credit to A10, who is just trolling. we're talking about a normal aircraft, not some super aircraft, or else the plane could just take off vertically. the Axle would have to take aton of punishment, and the engines would have to work perfectly for the plane not to simply crash. and then once the engine produces enough threat, where the wheels start skidding, its not consistent slip, you can get a second of real grip on one of the wheels and it would turn the plane to veer off the conveyor.

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Re: Anser me this

Okay new question: You are on a train moving at 2000km/h and you shoot a bullet going in the opposite direction at 2000km/h. What happens?

Not many people know this, but I own the first radio in Springfield. Not much on the air then, just Edison reciting the alphabet over and over. "A" he'd say; then "B." "C" would usually follow...

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Re: Anser me this

the train de-rails becouse theres no traintrack that can take trains at 2000km/h

also, theres no train that goes 2000km/h

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Re: Anser me this

-.- my post wasnt reffering to the mythbusters episode, just the op hmm

Your = possessive. As in, "your grammar sucks."
You're = you are. As in, "you're an idiot for not knowing the difference."

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Re: Anser me this

I can't believe I'm this silly. I'm not going to answer any of my posts!!

The core joke of Hitchhiker's Guide to the Galaxy is that of course no civilization would develop personal computers with instant remote database recovery, and then waste this technology to find good drinks.
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Re: Anser me this

Hmm..projectile motion. Aro the question is a bit vague. If the bullet is going at 2000kmph to the observer standing next to the train, then it will move at 2000kmph in the normal fashion of a projectile. If the bullet is travelling at 2000kmph as observed relatively from the person firing it, then the bullet will simple drop to the ground with no horizontal velocity.

Something interesting I realised when writing a programme on projectile motion with drag and wind: most people think the ideal angle to throw a ball to achieve greatest distance is at a 45 degree angle to the ground. This is true ignoring drag. In reality the ideal angle to achieve maximum range is actually 39 degrees tongue.

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That is rather useful information Pixies...I will take that to heart next time I play baseball in the outfield or football and I'm QB tongue

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Re: Anser me this

What I mean is that the firing mechanism of the gun fires the bullet at exaclty the same speed the train is moving.

My guess is that the bullet levitates in the air.

Not many people know this, but I own the first radio in Springfield. Not much on the air then, just Edison reciting the alphabet over and over. "A" he'd say; then "B." "C" would usually follow...

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hehe..no levitation. It would drop to the ground as if you simply dropped the bullet out of your hand when standing next to the railway track. Gravity in constantly acting on the projectile no matter what the horizontal velocity. This should help you understand that: http://www.youtube.com/watch?v=z24_ihikEqQ&feature=related

Pixies My pokemon brings all the nerds to the yard, and they're like you wanna trade cards?

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oh thx made me understand tongue.

New premise: You are going at lightspeed and you shoot a rocket out of the rocket. How would the rocket respond and move? And at what speed?

Not many people know this, but I own the first radio in Springfield. Not much on the air then, just Edison reciting the alphabet over and over. "A" he'd say; then "B." "C" would usually follow...

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Re: Anser me this

Pixies bad physics major!

Bad bad bad!!!!

Due to constant acceleration of the train and air pressure on the bullet the bullet would seem to never go up or forward, but down and backwards!

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Re: Anser me this

Errr..
Wasn't the premise that the train moved at a constant speed, rather than a accelerating one?

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Re: Anser me this

yes?

Not many people know this, but I own the first radio in Springfield. Not much on the air then, just Edison reciting the alphabet over and over. "A" he'd say; then "B." "C" would usually follow...

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114 Reply by Pixies (edited by Pixies 09-Mar-2009 19:25:42)

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Re: Anser me this

flint is just trolling X(!

Lateralis or sittingduck will give you a decent answer to that speed of light question. I've only ever read into relativity recreationally...but i think the main issue with that question is getting anything other than light travelling at the speed of light...they'll know tongue.

Btw, the speed of light depends on the medium through which it is travelling. In a vacuum it is 300,000km a second, but I do know light has been slowed to 45kmph (something along the lines of having it go through silicon at about 3 kelvin).

Pixies My pokemon brings all the nerds to the yard, and they're like you wanna trade cards?

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Re: Anser me this

Back to the future!!

Your = possessive. As in, "your grammar sucks."
You're = you are. As in, "you're an idiot for not knowing the difference."

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116 Reply by [TI] Sitting Duck (edited by [TI] Sitting Duck 09-Mar-2009 18:14:26)

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Re: Anser me this

The bullet on the train depends entirely on frame of reference

To someone sitting on the train the bullet will whizz past them (or into them) at 2000km/h. Remember that any inertial (i.e. non accelerating) frame of reference is indistinguishable to any other one, and if all the windows on the train were blacked out and there was no horizontal rocking motion because in the future when trains travel at 2000km/h they will be able to build tracks that well too tongue then someone sat on the non-accelerating train would not be able to distinguish between their state of constant velocity and being stationary. I don't tihnk I have said this very clearly and concisely, but basically to someone sitting on the train the bullet would act just as it would if both shooter and observer were standing outside on the grassy field.

To somebody standing outside on the grassy field though the bullet would appear to stay in mid air while the rest of the train moved past it. (and they therefore would still see it whizz past the observer on the train but because of the observer's motion, not the bullet)

A more interesting variation on this question would be if someone fired the bullet out of the window in a direction back along the length of the train, or even forwards in the same direction as the train was travelling. Would the bullet ever leave the gun? wink

As for speed of light question, where? Where?

Relativity is my pet hate of a physics subject though X(

tweehonderd graden, dat is waarom ze me mr. fahrenheit noemen, ik reis aan de snelheid van het licht, ik ga een supersonische man van u maken

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117 Reply by Pixies (edited by Pixies 09-Mar-2009 18:18:45)

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Re: Anser me this

"To someone sitting on the train the bullet will whizz past them (or into them) at 2000km/h. Remember that any inertial (i.e. non accelerating) frame of reference is indistinguishable to any other one, and if all the windows on the train were blacked out and there was no horizontal rocking motion because in the future when trains travel at 2000km/h they will be able to build tracks that well too tongue then someone sat on the non-accelerating train would not be able to distinguish between their state of constant velocity and being stationary. I don't tihnk I have said this very clearly and concisely, but basically to someone sitting on the train the bullet would act just as it would if both shooter and observer were standing outside on the grassy field.

To somebody standing outside on the grassy field though the bullet would appear to stay in mid air while the rest of the train moved past it. (and they therefore would still see it whizz past the observer on the train but because of the observer's motion, not the bullet)"

^^^ I've already said that fool, and in far few words tongue!

Aro's new question:

"New premise: You are going at lightspeed and you shoot a rocket out of the rocket. How would the rocket respond and move? And at what speed?"

Pixies My pokemon brings all the nerds to the yard, and they're like you wanna trade cards?

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Re: Anser me this

You expect me to read what other people have written? X(

As for the new question, firstly it is impossible to travel at light speed but let's say you are travelling at 0.99c compared to an observer in a rest frame (on Earth say). The rocket you fire will travel at the velocity you expect it to when you watch it from your rocket, to calculate it's velocity as observed from Earth you need to use the Lorentz transforms, in order to do that I would have to look them up which I can't really be bothered doing tongue

tweehonderd graden, dat is waarom ze me mr. fahrenheit noemen, ik reis aan de snelheid van het licht, ik ga een supersonische man van u maken

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119 Reply by [TI] Sitting Duck (edited by [TI] Sitting Duck 09-Mar-2009 18:40:43)

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When I said I couldn't be bothered doing it, I then decided to do it tongue

I am going to change the question a bit though because it is impossible for the original space ship to travel at c and would probably make the equations say something silly so say the spaceship is travelling at 0.9c and it fires a rocket at 0.5c, which classically looks like the rocket should travel at 1.4c.

If we say the Earth reference frame is S and the spaceship frame is S' and is travelling at 0.9c with respect to the Earth frame and we are trying to find the velocity of the rocket as viewed in the frame S

The relevant Lorentz transform is

v= (v' + u)/(1+[uv'/c^2])

where v is the velocity in S
v' is the velocity in S'
and u is the velocty of S' wrt S

=> v= (0.9c + 0.5c)/(1+0.9*0.5) = 0.966c

Therefore the rocket would appear to have velocity 0.966c as seen on Earth

tweehonderd graden, dat is waarom ze me mr. fahrenheit noemen, ik reis aan de snelheid van het licht, ik ga een supersonische man van u maken

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Re: Anser me this

The plane would travel forwards (along and off the conveyor belt) and take off because it relies on the thrust of the engines for forward movement and not friction between the ground and the tyre (plane wheels are free-wheeling and so the conveyor belt would have no effect on the plane's take-off, but it might kill your tyres).

The bullet would leave the gun and travel forwards untill it either ran out of forward momentum or hit something hard.

Same as the bullet, but sideways.

And if you turn on your headlights at the speed of light then they would turn on but the light would not get "there" untill you did, making them useless to you. tongue

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You are wrong about turning your head lights on at the speed of light. Light is special in that it travels at the speed of light when viewed in any inertial frame

tweehonderd graden, dat is waarom ze me mr. fahrenheit noemen, ik reis aan de snelheid van het licht, ik ga een supersonische man van u maken

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Re: Anser me this

Physics is so shit.

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Re: Anser me this

sad

Pixies My pokemon brings all the nerds to the yard, and they're like you wanna trade cards?

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Re: Anser me this

there is no spoon

The core joke of Hitchhiker's Guide to the Galaxy is that of course no civilization would develop personal computers with instant remote database recovery, and then waste this technology to find good drinks.
Steve Jobs has ruined this joke.

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Re: Anser me this

The cake is a lie!

..I wish i was good at maths sad

Your = possessive. As in, "your grammar sucks."
You're = you are. As in, "you're an idiot for not knowing the difference."

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