Trains

[:Ace:]

If you're standing up on a train and then you jump, will the train move underneath you?

[hevs]

Would this still apply if you happened to be standing on the top of the train ?!

[:Ace:]

Yeah! Would it?

[Sasha13]

What if you were running really fast towards the back of a moving train and then jumped? Would you then end up further down the train than if you had jumped from a standstill?

[Raj]

If you're standing on a planet (e.g. the Earth) that's revolving, and then you jump, will the planet move underneath you?

Of course not - same principle applies to a moving train.

[Mortartube]

Only if the train is stationary when you jump but starts to move off whilst you're in the air.

[Space]

if you were standing on the top of the train, it would be a bit different because the wind would push you towards the back of the train...

[Jay70]

I actually think you wouldn't land in exactly the same spot as you took off from.  Wether this was measurable of course would depend on how high you jumped, how fast the train was travelling and wether you could jump up at exactly 90 deg to the carriage floor.  As you leave contact with the carriage floor your forward velocity will initailly be the same as the moving carriage, agreed - but your forward momentum would surely slow due to the earth's gravitational pull opon your body  It would be very slight agreed - but only restricted by the height you could physically jump.  If you had a really high carriage and were able to jump to the top at exactly 90 deg to the floor then difference between the take of fand landing point of the person would be larger.

This question or a very similar question has been asked before and someone said you wouldn't move and gave an example of astronaughts in space craft floating and not being stuck to the back of the space craft as it was propelled along.  But of course there is no gravity pulling against them to oppose any lateral motion presented to their body so hence they wont slow down meaning the analogy in my opinion is invalid. 

As for jumping outside of the carriage the same applies except you would have to make an allowance for wind resistance.