Anonymous
Anonymous asked in Cars & TransportationRail · 2 months ago

What happens if you jump on a train when it's about to start moving forwards?

So a train is pulling into the platform. The doors open and you enter the train. The doors shut, and you stand up. Just when the train is about to pull out of the platform and move forwards, you jump, and then the train moves forwards.

Will you move with the train as you're in the air, or would you go flying through the train to the other end?

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• Fred
Lv 5
2 months ago

As long as the train is accelerating (which trains do not do in great degree) as you jump into the air on an accelerating train the train would move a few divisions of an inch forward while your air born body is not being accelerated by the energy from the accelerating floor underneath you. So if you were to jump precisely straight up, you would land a small fraction of an inch behind on the train floor as it moved forward by the very small difference of added acceleration while you were in the air.

Actually there is a small jolt as the engine takes up the small space in the couplers between following cars.  If you could jump precisely the very moment your cab was jerked into motion the movement under your feet  while in the air would be greater than any other acceleration the engine could provide and it could amount to somewhere up to perhaps 3 inches?  But passager trains are very cautious over such jolts and I think a movement of an inch would be on the rough side!

• 2 months ago

That could not happen in my country as the doors lock when the train moves.

• 2 months ago

A train doesn't accelerate that quickly. After getting off a train, I've walked (on the platform) alongside the train and been able to keep up with it for surprisingly far.

The answer is that you would not move with the train, but you would not go flying through the train to the other end. You would land over the same spot on the tracks where you were when you jumped. You would be in almost the same spot in the train as where you jumped, only a few inches or centimeters closer to the other end of the train, because that is as far as the train would have moved. (This is assuming you have enough room; depending on where you do it, you may hit something first.)

The real problem is when you land. Because the train is moving forward and you aren't, when your feet hit the floor, the train pulls them forward, but the rest of your body keeps moving backwards relative to the train, so you fall over. If you want to try the experiment, do it somewhere that you can grab something for balance when you hit the ground.

• 2 months ago

For your particular question, the train would move under your feet a little as the atmosphere in the train is not moving with it.  But why doesn't the earth move under your feet when you jump us as it is rotating rather quickly.  If you put a 6' rotating ball under your feet and jumped up the ball would move and you would land on a different spot on it.  When the entire atmosphere around the earth moves with the earth it carries you along with it; not so in the train.

• 2 months ago

You slide under the train and get caught up in the wheels.

• 2 months ago

If the train was stationary when you jumped, then your position inside the train where you land will be "backward" by whatever small distance it moved while you were in the air.

In other words, you were in the air a couple seconds.  How far do you think a train can move from a dead stop in a couple seconds?  Perhaps a foot?  Probably less.

The only way you could go "flying to the other end," is if the train accelerated fast enough to create fatal G-forces for everyone else in it besides you.