[Seany (OP)]

If you have a passenger inside a train, and he drops a ball.. If you neglect air resistance, would the ball be horizontally motionless to the passenger?

[RD]

It will drop vertically from the passenger's viewpoint if the train is travelling at a constant speed on straight track (or stationary).

If the train is accelerating or decelerating it won't, (NB: train going round a bend counts as accelerating because it's changing direction even if it's speed is constant).

[Seany (OP)]

Thanks. And if it were to have air resistance. It would appear from the passenger's point of view to be going backwards.

But from an observers point of view, it would go in the direction of the train, but with a smaller velocity?

[RD]

... And if it were to have air resistance. It would appear from the passenger's point of view to be going backwards.

Only if there was air flow through the train carriage, in a sealed carriage (no draughts) it would still drop vertically from the passenger's perspective if the train's speed was constant and the train tracks straight.

[Seany (OP)]

Bugger [] I meant that he drops it outside the window

[yor_on]

It would initially have the same speed as the train, and to the 'train dropper' seem to fall 'straight down' ignoring all resistance now. Same as inside the carriage in fact

From a stationary observer watching the train pass, it would move in a arc, now assuming that the train doesn't have a velocity allowing the ball to reach orbital speed. If you include air resistance it will also slow down relative both observers, and as you say move backwards from the train droppers POV. Assuming that the 'train dropper' defines the train as stationary he will now be in need of a strong drink to cool his nerves as everything moves the wrong way

I think?

[Seany (OP)]

[]

[lightarrow]

If you have a passenger inside a train, and he drops a ball.. If you neglect air resistance, would the ball be horizontally motionless to the passenger?

Galilei made this and other experiments "below deck" (" sotto coverta" in his language) inside a ship and concluded that, as long as the ship is moving straight at constant velocity, you can't notice that you are moving. It's called "Galileian principle of relativity" and it's extremely important in physics.