How does running in a moving train affect race times?

[dzoni]

Property of walking is a constant contact with the surface (base of the train).
Property of running is NOT a constant contact with the surface (base of the train).

When walking at the same speed we should expect the same result for our hypothetical walker to walk across certain distance (within moving train) regardless if he walks in counter direction of trains motion or in the same direction of trains motion, because our walker is constantly connected with the surface of a moving train with one leg at least.

However, having in mind property of running which presumes spending some 50 % of the entire race time in the air (fully disconnected from the surface of the train - with both lags) we must expect quite different results for two different races :
A) The first race : Running in counter direction of trains motion
B) The second race : Running in the same direction of trains motion

So, if we measured the time that needs to some runner (assuming that he runs at the same speed all the time) to cross certain distance when running in a moving train, we should expect a different results comparing the situation in which he runs in counter direction of trains motion versus when he runs in the same direction of trains motion. Let's say that our runner runs 30 km/h (in absolute terms a.k.a using his muscles in the same manner as he would do when running within inertial frame of reference, that is to say : in a NON moving train or on any other NON moving surface, so that he reaches the speed (in such circumstances (within inertial frame of reference)) of exactly 30 km/h), and the train is moving 3 km/h.

Now, how would you calculate the time needed for him to cross let's say 100 m distance :
A) When running in counter direction of train's motion
B) When running in the same direction of train's motion

 

[phyzguy]

I think you have not understood that all motion is relative. There is no "universal state of rest" that you are in motion with respect to. For example, the Earth's rotation causes the Earth's surface to move at hundreds of miles per hour (depending on your latitude). By your logic you should run significantly faster when running East than when running West. Do you notice this effect?

 

[Ibix]

As @phyzguy says, that's not the way it works.

An easy experiment is to take a train with a friend. Sit opposite each other and throw a ball back and forth. Is throwing one way harder than the other? By the reasoning in the first post, it should be. Do you think it will be?

 

[PeroK]

Property of walking is a constant contact with the surface (base of the train).
Property of running is NOT a constant contact with the surface (base of the train).

When walking at the same speed we should expect the same result for our hypothetical walker to walk across certain distance (within moving train) regardless if he walks in counter direction of trains motion or in the same direction of trains motion, because our walker is constantly connected with the surface of a moving train with one leg at least.

However, having in mind property of running which presumes spending some 50 % of the entire race time in the air (fully disconnected from the surface of the train - with both lags) we must expect quite different results for two different races :
A) The first race : Running in counter direction of trains motion
B) The second race : Running in the same direction of trains motion

So, if we measured the time that needs to some runner (assuming that he runs at the same speed all the time) to cross certain distance when running in a moving train, we should expect a different results comparing the situation in which he runs in counter direction of trains motion versus when he runs in the same direction of trains motion. Let's say that our runner runs 30 km/h (in absolute terms a.k.a using his muscles in the same manner as he would do when running within inertial frame of reference, that is to say : in a NON moving train or on any other NON moving surface, so that he reaches the speed (in such circumstances (within inertial frame of reference)) of exactly 30 km/h), and the train is moving 3 km/h.

Now, how would you calculate the time needed for him to cross let's say 100 m distance :
A) When running in counter direction of train's motion
B) When running in the same direction of train's motion

If you are on a train and toss a coin it goes straight up and down normally relative to you. It doesn't need to be attached to the train to keep moving at the constant speed of the train.

Your question, therefore, is based on a misapprehension about constant motion.

In addition, the Earth is rotating West to East, but you don't notice this if you run on the Earth's surface.

 

[dzoni]

+phyzguy - Why don't you concentrate strictly to my question? Why drawing such an epochal inferences before answering such a simple question? If our runner runs 30 km/h it takes 12,04 sec for him to cross 100 m within inertial frame of reference. If our train is moving 3 km/h after 12 seconds our train is going to traverse roughly 10 m. So, it seems that our runner is going to cross 100 m in about 11 seconds when running in counter direction of trains motion, and he is going to cross 100 m in about 13 seconds when running in the same direction of trains motion, due to the property of running (which is "half flying-half walking" phenomena, so to speak). Isn't that so? I am only interested in finding out if there is some particular reason (some physical law or an effect) which would make my simple math groundless?

 

[dzoni]

Oh, it seems that we have some problems here with a bunch of prejudices...Can't you just concentrate to my question without making unnecessary references to heliocentric theory?

 

[Ibix]

Why don't you concentrate strictly to my question?

Because the wider implications of your thinking should make it instantly clear that you are wrong.

Isn't that so?

Clearly not, as all three counter examples you have been given show.

I am only interested in finding out if there is some particular reason (some physical law or an effect) which would make my simple math groundless?

Galilean relativity.

Oh, it seems that we have some problems here with a bunch of prejudices...

It isn't prejudice, so much as three and a half centuries of experimental testing.

 

[dzoni]

It isn't prejudice, so much as three and a half centuries of experimental testing.

What experimental testing? Can you show me some peer-review work which is able to disprove validity of my simple math (see above) and simple irrefutable logic which lies behind this simple math?

 

[FranzDiCoccio]

Hi,

I think that your initial hypothesis that running is different from walking does not make sense.
What would happen if you jumped up and down on the train? You would loose contact with the train floor roughly for the same amount of time as when you take a "running step". Would that change your velocity relative to the train (which is zero)? The answer is no.
Why would it change if it's not zero, then?

If our runner runs 30 km/h it takes 12,04 sec for him to cross 100 m within inertial frame of reference. If our train is moving 3 km/h after 12 seconds our train is going to traverse roughly 10 m. So, it seems that our runner is going to cross 100 m in about 11 seconds when running in counter direction of trains motion, and he is going to cross 100 m in about 13 seconds when running in the same direction of trains motion, due to the property of running (which is "half flying-half walking" phenomena, so to speak). Isn't that so? I am only interested in finding out if there is some particular reason (some physical law or an effect) which would make my simple math groundless?

I did not check your maths, but its correctness has nothing to do with the cause of motion. The velocity (vector) of the guy is summed to that of the train according to Galilean relativity whether he's running, walking, crawling or moonwalking. The only thing that matters is the velocity of the guy relative to the train, and the velocity of the train itself.

 

[FranzDiCoccio]

Another counterexample

suppose your runner is chasing another guy on a bycicle. They are both on the train, and they are moving at the same velocity relative it (their distance on the train remains the same).
Bicicle wheels are always in contact with the floor. The guy is "half flying", as you put it. Your thinking would imply that two different things happen to them.
That is not the case.

 

[dzoni]

The only thing that matters is the velocity of the guy relative to the train, and the velocity of the train itself.

Maybe we should reformulate my question :
If our runner flies 30 km/h above the moving train which travels 3 km/h what would happen (how much time would it take for him to fly across 100 m length of a moving train) :
A) After flying in counter direction of train's motion 30 km/h
B) After flying in the same direction of train's motion 30 km/h

 

[Ibix]

It isn't prejudice, so much as three and a half centuries of experimental testing.

What experimental testing? Can you show me some peer-review work which is able to disprove validity of my simple math (see above) and simple irrefutable logic which lies behind this simple math?

Any school level physics textbook ought to cover this. Certainly any university level textbook will.

Edit: Also, we can run west, as phyzguy pointed out.

 

[Ibix]

If our runner flies 30 km/h above the moving train which travels 3 km/h

30 km/h with respect to what? 3km/h with respect to what? You will get different answers depending on your answers to this.

Edit: and 100m measured by who? Someone on the train using rulers attached to the train, or someone on the ground using rulers attached to the ground?

 

[FranzDiCoccio]

The only thing that matters is the velocity of the guy relative to the train, and the velocity of the train itself.

Maybe we should reformulate my question :
If our runner flies 30 km/h above the moving train which travels 3 km/h what would happen (how much time would it take for him to fly across 100 m length of a moving train) :
A) After flying in counter direction of train's motion
B) After flying in the same direction of train's motion

The mode of motion of the guy (flying, crawling or walking) would not matter. The only thing that matters is the frame of reference. If his velocity is measured in the train frame of reference
A) a guy on the platform would see him moving at 27 km/h towards the back of the train
B) a guy on the platform would see him moving at 33 km/h towards the head of the train

Edit: as Ibix points out, you should be more precise and specify the frame of reference where your velocities are measured.

 

[dzoni]

30 km/h with respect to what? 3km/h with respect to what?

See my opening post!

 

[dzoni]

The mode of motion of the guy (flying, crawling or walking) would not matter. The only thing that matters is the frame of reference. If his velocity is measured in the train frame of reference
A) he moves at 27 km/h towards the back of the train
B) he moves at 33 km/h towards the head of the train
both A) and B) are relative to someone standing on the platform.

We are not interested about someone who is standing on the platform.
Yes, if his velocity is measured in the train frame of reference
A) he moves at 27 km/h towards the back of the train
B) he moves at 33 km/h towards the head of the train

I agree with you!
Does Galileo agree with two of us?

 

[russ_watters]

It isn't prejudice, so much as three and a half centuries of experimental testing.

What experimental testing? Can you show me some peer-review work which is able to disprove validity of my simple math (see above) and simple irrefutable logic which lies behind this simple math?

When Galileo figured this out, there was no such thing as per reviewed research, but you can easily test this principle for yourself next time you are in a car, train or plane.

 

[Ibix]

See my opening post!

In that post you refer to some absolute motion. There is no such thing, so it does not address my questions. Is he doing 30km/h relative to the ground, the train, or something else?

Four posters have now pointed out your errors and the obvious inconsistencies with every day experience. Please stop and think. Or better yet, actually do the experiment I proposed in #3. You'll see there's no difference between throwing a ball forwards or backwards in the train, and hence that your entire argument is wrong.

 

[FranzDiCoccio]

Does Galileo agree with two of us?

I'd say that what I say is in agreement with Galilean relativity.
I'm not exactly sure about what you're saying. The whole thing about "half walking half flying" is entirely flawed. Your frames of reference are unclear, and we have to guess what you mean.

And I think Galileo would agree with me on that. See his comments about flies and butterflies on the boat ("Dialogo sopra i due massimi sistemi del mondo"). Trains did not exist at the time, so he thought of performing these experiments inside the hold of a ship.

 

[Ibix]

Does Galileo agree with two of us?

Taking Franz' assumption that you meant "30km/h with respect to the ground", yes. But that's not the same as the running on a train scenario, where the guy (somewhat improbably) does 30km/h with respect to the train. There, you would disagree with Galileo and common sense.

 

[dzoni]

In that post you refer to some absolute motion. There is no such thing, so it does not address my questions. Is he doing 30km/h relative to the ground, the train, or something else?

Let's quote this passage from my opening post :

So, if we measured the time that needs to some runner (assuming that he runs at the same speed all the time) to cross certain distance when running in a moving train, we should expect a different results comparing the situation in which he runs in counter direction of trains motion versus when he runs in the same direction of trains motion. Let's say that our runner runs 30 km/h (in absolute terms a.k.a using his muscles in the same manner as he would do when running within inertial frame of reference, that is to say : in a NON moving train or on any other NON moving surface, so that he reaches the speed (in such circumstances (within inertial frame of reference)) of exactly 30 km/h), and the train is moving 3 km/h.

Maybe i should make my bold words even clearer : If you doubt that our runner can maintain the same speed all the time, then imagine some robot which is programed to move absolutely evenly, so that we can substitute our runner with such a precise mechanical device which is going to provide for us constant motion (the same speed)...So it's about moving at the same speed (calibrated within inertial frame of reference), and not about absolute motion...

 

[FranzDiCoccio]

We are not interested about someone who is standing on the platform.

What do you mean? I am. And you too should
Again. Please think carefully about this and ask a clear question.

Also, please note that I slightly edited my answer that you agreed with, in order to make it more clear. Velocity is always referred to some frame of reference in which you measure it. You should specify it.

 

[dzoni]

And I think Galileo would agree with me on that. See his comments about flies and butterflies on the boat ("Dialogo sopra i due massimi sistemi del mondo"). Trains did not exist at the time, so he thought of performing these experiments inside the hold of a ship.

I have this book here with me, laying on the table right in front of me, don't worry!
And i can tell you : Galileo was wrong on this subject, absolutely wrong!

 

[Ibix]

the same speed

The same speed relative to what? You clearly aren't going to answer this question because if you do your argument falls to pieces.

I'm dropping out of this conversation. Good night, all.

 

[FranzDiCoccio]

Wrong about what, exactly?
About the flies he simply pointed out that the way they move relative to the boat does not depend on the fact that the boat is moving (at a constant velocity wrt an inertial frame)

Anyway, Galilean relativity is pretty bulletproof, unless the bullet moves at a significant fraction of the velocity of light.
If you think it is wrong, I am afraid you did not understand it.Since you are not making yourself clear, I suggest that this post is closed, because we're going in circles.

 

[Doc Al]

However, having in mind property of running which presumes spending some 50 % of the entire race time in the air (fully disconnected from the surface of the train - with both lags) we must expect quite different results for two different races :
A) The first race : Running in counter direction of trains motion
B) The second race : Running in the same direction of trains motion

Unless you are somehow considering air resistance (in an open train car, perhaps), why would you think this? Being "disconnected" means nothing -- you just need enough connection to maintain your speed relative to whatever you're running on -- whether a train or the Earth is irrelevant.

 

[Doc Al]

Before you close this post

Too late. Thread closed for moderation.

 

[Dale]

We have deleted several posts that strongly violated the rules, and the thread will remain closed.