The next conumdrum following the "Plane take off?" resolution:

[FP]

wouldn't gravity also have an effect (albeit a very minor one) on your forward momentum?

 

[DanFungus]

free/force body diagram.

If there is air/wind resistance, you will "move" towards the back of the train (really it will just be that the train's speed remains constant and you slow down) and if there is no air/wind resistance you will land in the same spot (assuming the distance is short enough to say the ground is perfectly flat. If it's high enough to make the earth's curvature come into play, you will move toward the back of the train).

 

[Connoisseur]

Originally posted by: Beattie
I thought of another example.

If you are standing on Earth and jump do you magically move west?

The earth is rotating below you after all.

You're rotating along with the earth. Once again, sans wind resistance you'll land at exactly the same spot.... no matter how high you jump.

 

[everman]

it doesn't take off

 

[SunnyD]

Originally posted by: Connoisseur

Originally posted by: Beattie
I thought of another example.

If you are standing on Earth and jump do you magically move west?

The earth is rotating below you after all.

You're rotating along with the earth. Once again, sans wind resistance you'll land at exactly the same spot.... no matter how high you jump.

You sure about that? Sans wind resistance, no matter how high you jump you say?

What happens when you jump high enough to exit the atmosphere and come close enough to any heavenly body to be affected greatly by their gravitational force? Yeah, didn't think so.

Despite the overwhelming incidence of the Earth's gravity on a body, gravitational forces from all over the universe are at work. You will NEVER land in the same place twice (aside from infinite entropy).

 

[edro]

Originally posted by: E equals MC2

LOL

 

[OdiN]

What would be cool (assuming no resistance forces) would be to run as fast as you can, and then jump. You could move forward.

 

[YOyoYOhowsDAjello]

Originally posted by: torpid

Originally posted by: YOyoYOhowsDAjello

Originally posted by: E equals MC2

You mean to tell me if I jump/launched to 200 yards, I would land in the roughly same spot? (sans wind resistance), never losing the velocity of the train? What if I jump 500 yards, 1000, 2000? I will NEVER lose the velocity of the train?

If we're ignoring wind resistance and taking out "curvature of the earth" type requirements and you don't reach escape velocity of the earth's gravitational pull, then I think that takes care of most of the effects that would prevent you from landing back in the same spot.

Except for the fact that it is quite difficult to jump perfectly straight up into the air.

And the tracks aren't going to be straight and the train is going to have minor fluctuations in speed as it moves and you could add many other things to the problem that would cause these kinds of differences. It's also quite difficult to jump 2000 yards into the air.

 

[Mo0o]

lol someone is not so good at physics

 

[silverpig]

Neglecting all forces that may cause you to not land in the same spot, you will land in the same spot.

 

[cKGunslinger]

PHAIL

 

[torpid]

Originally posted by: YOyoYOhowsDAjello

Originally posted by: torpid

Originally posted by: YOyoYOhowsDAjello

Originally posted by: E equals MC2

You mean to tell me if I jump/launched to 200 yards, I would land in the roughly same spot? (sans wind resistance), never losing the velocity of the train? What if I jump 500 yards, 1000, 2000? I will NEVER lose the velocity of the train?

If we're ignoring wind resistance and taking out "curvature of the earth" type requirements and you don't reach escape velocity of the earth's gravitational pull, then I think that takes care of most of the effects that would prevent you from landing back in the same spot.

Except for the fact that it is quite difficult to jump perfectly straight up into the air.

And the tracks aren't going to be straight and the train is going to have minor fluctuations in speed as it moves and you could add many other things to the problem that would cause these kinds of differences. It's also quite difficult to jump 2000 yards into the air.

Ah, those are good points too. I did a short circuit evaluation and my brain returned FALSE after thinking just about the jumping straight up. Your brain appears to be more advanced and capable of evaluating further.

 

[hiromizu]

No because there's an elephant in the way.

 

[FleshLight]

Assuming the train travels in a straight line and neglecting air friction, terminal velocity, escape velocity, lift, wind resistance, coriolis force, pressure gradients, temperature gradients, fracture mechanics, deformation mechanics, etc, you will land in exactly the same spot if you jump straight up.

 

[Evadman]

Originally posted by: silverpig
Neglecting all forces that may cause you to not land in the same spot, you will land in the same spot.

And neglecting all forces that may cause me not to have a non-zero bank account, i will have a non-zero bank account.

that is the... damn I can't even come up with a word for it. WTF man, WTF?!

 

[randay]

Originally posted by: E equals MC2
If I?m standing inside a walled-in cabin of a train going 50 mph and I jump, I would NOT suddenly land in BACK of the cabin because I?m MOVING with the train.

Now, what if I was standing on an empty, open-faced freight car of the train? (just the flat surface)

1. If I jump, would I suddenly land towards the back of the train?
2. If you said no, what if I jumped 30 ft in the air? Would I land back on the EXACT same spot as I left? At what point do I lose my velocity WITH the train?

You mean to tell me if I jump/launched to 200 yards, I would land in the roughly same spot? (sans wind resistance), never losing the velocity of the train? What if I jump 500 yards, 1000, 2000? I will NEVER lose the velocity of the train?

1. is the train moving backwards, or forwards?

2. what is the altitude of the train? why are you standing on my dog? exactly how much velocity do you own, and do you keep it in your front pocket or back pocket?

 

[jagec]

OP, for having such a physics-related username, your grasp of classical physics is a little weak.

 

[silverpig]

Originally posted by: Evadman

Originally posted by: silverpig
Neglecting all forces that may cause you to not land in the same spot, you will land in the same spot.

And neglecting all forces that may cause me not to have a non-zero bank account, i will have a non-zero bank account.

that is the... damn I can't even come up with a word for it. WTF man, WTF?!

Well that's what all of these "what if?" physics threads degenerate into. Someone asks a question and says to neglect some forces. Someone then replies with an answer that uses some very small correction, negligible, but non-zero. Someone else then adds some other small corrections, then everyone says it'd take a supercomputer and a team of physicists to calculate the exact answer.

Most physics questions aren't "what happens if...", they are "including these effects, what is the outcome when..."

 

[Evadman]

You are currently moving at 3.14159 * 93,000,000 * 2 = 584335740 / 365.25 / 24 = 66659 MPH (+/- 2% due to elongation) around the sun due to the earth's orbit. In other words, if the earth were to be suddenly stopped, you would leave the earth's surface at 66659 MPH, leave the atmosphere in 3.3 seconds then smash into the moon 3.58 hours later.

Now, if you were on the side of the Earth facing away from the orbital motion, your head would decelerate from 66659 MPH to 0 in the distance of your height. Assuming you are 6' tall, you would experience enough G force to turn your head into a 1 or 2 atom thick covering on the surface of the earth. Your head, at 8 KG, would dissipate 1/2*8*29,799.2^2 = 3,551,969,282.56J, or about the same amount of energy as 2 fully loaded semi-tractor trailers in a head on collission at over 1,000 MPH with your head in the middle.

Just thought you should know.

 

[Eeezee]

Originally posted by: E equals MC2
If I?m standing inside a walled-in cabin of a train going 50 mph and I jump, I would NOT suddenly land in BACK of the cabin because I?m MOVING with the train.

Now, what if I was standing on an empty, open-faced freight car of the train? (just the flat surface)

1. If I jump, would I suddenly land towards the back of the train?
2. If you said no, what if I jumped 30 ft in the air? Would I land back on the EXACT same spot as I left? At what point do I lose my velocity WITH the train?

You mean to tell me if I jump/launched to 200 yards, I would land in the roughly same spot? (sans wind resistance), never losing the velocity of the train? What if I jump 500 yards, 1000, 2000? I will NEVER lose the velocity of the train?

Once you jump high enough, the coriolis effect is no longer negligible. In a rotating reference frame (Earth) you will not land in the same spot regardless of air resistance. There is a slight east/west deflection depending on whether you were dropped from 300 feet or if you jumped to 300 feet.

The Earth rotates toward the East, so if I am dropped from 300m I am deflected slightly to the west (I will land further west than I expected). There are additional effects that cause the you to be deflected slightly to the east if you jump from 0m to 300m and land back at 0m (there is also a factor of 4 difference in magnitude, but I forget if the drop is 4x greater or if the fall is 4x greater). This is a problem you do in Goldstein's Classical Mechanics and it's a real classic.

If the Earth is not rotating and there is no air resistance, then if you jump 2000 yards into the air you will NEVER lose the velocity of the train. Why would you? There is no force acting on you except for gravity, which only changes your "up/down" velocity. As such, your velocity will point in the same direction as the train with the same magnitude as well.

If there is air resistance and the front of the train is open and you jump a couple of feet in the air, then you will notice that you didn't land in the same spot. You won't necessarily be thrown to the back of the train (but this all depends on how fast the train was moving in the first place - the faster the train is moving, the more air resistance and thus the further you would be thrown to the back of the train).

 

[Eeezee]

Originally posted by: Evadman

Originally posted by: silverpig
Neglecting all forces that may cause you to not land in the same spot, you will land in the same spot.

And neglecting all forces that may cause me not to have a non-zero bank account, i will have a non-zero bank account.

that is the... damn I can't even come up with a word for it. WTF man, WTF?!

That's what the OP specified though, the OP just didn't realize it at the time.

OP's post (summarized): I am on a moving train. There are no forces acting on me except for gravity. I jump. Do I land on the same spot regardless of how high I jump?

The answer: Yes, if there are no forces acting on you then you should land in the same spot. If the Earth is rotating, you will experience a slight deflection and not land in the same spot. It's as simple as that.

 

[Evadman]

you have exactly the wrong handle.

 

[warmodder]

Motion in the X does not affect motion in the Y (someone must have written that though). That said irl there are other forces acting (wind resistance for one) that will cause you to not land in the same spot.

 

[Ruptga]

In a vacuum, I believe you could jump as high as you wanted (assuming of course you went 90 degrees straight up in the first place) until you either got so high that you escaped gravity, or the curvature of the earth/moon/wherever you are started to mess with stuff.

 

[sonambulo]

Originally posted by: E equals MC2
*snip*

I used to hop trains all the time and we tested this out many times in wide open boxcars. If you jump while the train is moving you will land in the same spot.

If you jump while the train is moving and you are shitfaced on wild turkey you will land somewhere near the back of the car.