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NJL72413

A Shot From The Back Of A Train?

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I dunno if there's really much to debate, but it's an interesting question at least.

 

So the typical speed of a bullet shot from a rifle is 1000 meters per second (or so says wikipedia). If you are at the back of a train or air plane, or whatever your traveling in and you are travel at 1000mps and you shoot your bullet, does it move at all? Will it even leave the gun? If it leaves the gun than how far does it go? Does it fall straight down?

 

Lol I wanna know!

 

This might not be in the right forums, but whatever, it's an interesting question.

 

 

THIS IS NOT BEING UNDERSTOOD - Here is the simplest version possible -

 

Object 1 is being carried by object 2. Object 2 is moving at 1 unit per second in a straight line, we assume it's going forward. Object 1 begins to move in the opposite direction (backward) at 1 unit per second. At what speed is unit 1 moving, and if it is moving, is it moving forward or backward?

Edited by NJL72413

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It would move the same speed as you are. It wouldn't look like it's moving (just like any other time something is moving the same speed as you) to you, but it would to others. >.<

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That's doesn't sound right. An objects speed = Initial speed +/- speed of object it's fired from. So if you're going 1000mps and you fire a bullet at 1000mps from the back of the train isn't the bullet doing 1000-1000=0mps?

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The bullet would still travel at normal speed. The bullet and the gun are moving with the train, so they might as well be standing still. If you were to fire a 1000m/s bullet from outside the train, the bullet would probably float outside of the window.

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No it would be going the same speed you are, so it wouldn't look like it was moving at all. Take riding in car for example. If a car is going 30 mph, then the people in it are also traveling at 30 mph even though it doesn't look like they are moving. How ever when you slam on breaks everyone in the car shifts forward because they are still traveling at 30 mph when you hit the brakes. It would the same case for the rifle. It wouldn't like it was moving because it is going the same speed as the train.

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Well, I don't know about bullets. But on television a few guys tried to fire a torpedo-like thing whilst driving. When shooting forward, it was the same, when shooting backward however, the bars immediately fell on the ground. It was like they just fell off the car. Of course a bullet leaves the gun with much more power and such, so it might keep flying.

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It's wouldn't look like it was moving from whose perspective? The person how shot it? or someone watch from the outside?

 

It wouldn't like it was moving from anyone's perspective. I mean the train would be moving, but the bullet would look as if it was suspended in midair.

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If the gun was on the train when it was fired, I imagine it would go faster than the train in question. It would already be travelling at 1km p/s, so the boost of the ignition would add to that.

 

That was shooting foward.

 

Backward, I'd assume it would go slightly under 1km p/s.

Edited by Dad

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It's just like how people can hear each other on a supersonic jet. The person was on the train when they shot the gun, so the bullet would just be going at its normal speed plus the speed of the train. It would look like it was going at normal speed to those on the train(what little of it can be seen that is).

 

EDIT: Lol Dad beat me to it.

Edited by Superkid711

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I have extremely simplified the question in the first post. Please look at it and maybe you will see what I mean, because no one is giving the answer to the question I'm asking. Everyone is giving the answer to another question which I already understand.

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It keeps moving in the same direction it was launched in. If a train instantly changed direction at the exact moment the bullet was fired, the bullet would appear to be going even faster.

 

However, if Object 2 happens to be rolling or walking on the ground, then the train's direction wouldn't effect the object's speed at all because it's in contact with the train.

Edited by Superkid711

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Object 1 is being carried by object 2. Object 2 is moving at 1 unit per second in a straight line, we assume it's going forward. Object 1 begins to move in the opposite direction (backward) at 1 unit per second. At what speed is unit 1 moving, and if it is moving, is it moving forward or backward?

 

 

Object 1 is going nowhere at 0 units per second(in relation to earth i guess) until it reaches the end of object 2 at which point it is moving backward at 1 unit per second, assuming object 2 doesn't stop like with a wall or something

 

or at least that is how i see it

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Your question was not very clear. Are both the bullet and the object you are riding in going in the same direction (I understand they are at the same speed)?

 

It is an impossibility with the current design of a plane or train to fire from it while going at those speeds. If a bullet was fired along the same path as the object you are riding in, it would appear to be along side of you (assuming it was fired along side of you to begin with). As both objects are moving in the same direction at the same speed they will maintain the same distance from each-other.

 

If the bullet is fired in the direct opposite direction from the object you are traveling in, the bullet will appear to be going twice as fast as it really is (as you are moving away from it at the same speed it is traveling). Although it is actually traveling at half the speed you are witnessing travel at.

 

 

So it would just float in the air at the point from which it was shot?

 

If the object it was traveling in stayed at the same speed of the bullet, it would appear to float in the air. If the object changed from the path the bullet was traveling on, the bullet would hit (and/or go through) said object.

 

I was wondering, is the air inside the object you are in still (i.e. no fans etc.)? If so, then the bullet could travel at the same height, as there would be no air resistance to bring it down (the wall in front and to the sides of the bullet would divert the air away from the bullet thus not forcing the bullet to "go through" the air).

 

~John

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In your simplified question you provide that it is moving at one unit per second. So I assume that's the answer. (lolperfectionist)

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Everything in that place you are travelling in be it train/plane is moving at the same pace, so your bullet is already moving at whatever speed your going at.

 

Don't take me for certain on this, but I don't think it applies when your going vertically up, like in a rocket because of the immense G-Forces you feel etc.

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OMG - what are they teaching you kids in science these days?

 

Only one person seems to have made any sense in all the answers above.

 

I'll clarify...

 

The bullet, shot out the back of the train, will join all the other stationary scenery in whizzing back past the train at 1000m/s. From the point of view of someone stationary, say standing in that scenery, the bullet will have zero velocity and will behave no differently than if it had just been let go of by someone standing still, i.e. it will fall directly toward the ground.

 

In the converse scenario, someone gently tossing a bullet into the path of a train moving at 1000m/s will cause the same amount of damage as firing a bullet at 1000m/s directly at a stationary train.

 

Back when I was a lad.... this stuff would have been taught to anyone studying physics or maths by age 12 or 13.

 

The following answers are completely incorrect:

 

The bullet would float in mid-air (miraculously defying the laws of gravity)

No such designs are possible with current technology (run forwards and throw a ball backwards - hey presto - technology demonstrated)

The bullet would continue in the direction it was launched in (again miraculously defying the laws of gravity)

The bullet would have slightly less velocity than 1km/s (1000 - 1000 = slightly less than 1000?)

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And remember, we are also travelling at X speed if you account for the rotation of the earth >.<.

 

~Razorlike

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The problem is the reference frame. It's all relative to the observer. Before asking the question, you need to establish a reference frame for this to make sense

 

Relative to the shooter, the bullet will appear to be moving at 2000m/s velocity.

 

Relative to someone observing stationary from the ground, it will appear to move 1000m/s in the direction it's fired at.

 

Relative to the plane, it will appear to be stationary.

 

Actually I'm pretty sure I'm wrong. Relative velocity was never my strong points.

 

What you should take from my post though is that you have to establish a reference frame relative to an observer. It'll be different to different observers. For example, if you watch someone drive in a car, they appear to be moving away from you but to the person in the car, you appear to be moving away from them.

 

I also read your post again for the simplified part. Here's the solution.

 

velocity of 2 = 1 m/s

velocity of 1 = -1m/s because it's going in the opposite direction. Velocity is a vector.

 

Now the velocity of 1 relative to 2 is v1 - v2 = relative velocity.

 

-1 - 1 = -2.

 

So the velocity of the object will appear to move 2m/s away from the thrower.

Edited by Gavin

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This is really quite simple. I'm going to assume you meant they were both traveling at 1000M/s, so in that case:

 

If you fire it off the back of the train, backwards, it will go away from the train at 1000M/s, which is 0M/s in relation to the ground. So it'd fall straight down.

 

If you fired it off of the front of the train, forwards, it'd again move away from the train at 1000M/s, and would be moving at 2000M/s in relation to the ground.

 

It's really not that complicated.

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Are you serious?

 

It would fire as normal. And look normal to.

 

Train is going < way. Bullet goes > way. No effect on each other.

 

The speed of the train doesn't make the bullet faster or slower.

Edited by Zachorayi

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Thank you SlashingUK!!!!!!

 

Finally someone who understood my question!

 

That was the conclusion I came to as well. Since Object 1 is already moving at 1mps forward, as soon as it begins it's travel backwards at 1mps it is going 0mps and it falls to the ground, or if we carry out this experiment in space it just stays at the exact point (or pretty close) to where it began moving backwards.

 

So that means that beginning to travel backward at 1mps in that situation is the same as stopping instantly. If that is true than was it ever going at 1mps (backwards), or did it simply stop. Was all the energy that was put into that 1mps (backwards) lost because it simple stopped moving? If an object was somehow on the ground at the exact point where the bullet began moving at 1mps (backward), would that object feel the same effect as if the bullet had hit it at 1mps from the ground beside it? Does this bullet, now traveling at 0mps have enough energy to do anything more than bounce off the ground it hits?

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Thank you SlashingUK!!!!!!

 

Finally someone who understood my question!

 

That was the conclusion I came to as well. Since Object 1 is already moving at 1mps forward, as soon as it begins it's travel backwards at 1mps it is going 0mps and it falls to the ground, or if we carry out this experiment in space it just stays at the exact point (or pretty close) to where it began moving backwards.

 

So that means that beginning to travel backward at 1mps in that situation is the same as stopping instantly. If that is true than was it ever going at 1mps (backwards), or did it simply stop. Was all the energy that was put into that 1mps (backwards) lost because it simple stopped moving? If an object was somehow on the ground at the exact point where the bullet began moving at 1mps (backward), would that object feel the same effect as if the bullet had hit it at 1mps from the ground beside it? Does this bullet, now traveling at 0mps have enough energy to do anything more than bounce off the ground it hits?

 

You answered your own question. It's traveling at 0mps. If you got hit by a bullet that fell maybe 5 or 6 feet, would you be hurt? No.

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For the sake of settling the argument, you may want to look it up on Mythbusters ...

 

If they haven't solved this one already, there is prolly a discussion group about it.

 

>.<

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