Coming back from NYC on Amtrak, I decided to try something that I’ve always wanted to do. I stood in my roomy sleeper car and while the train was zooming thru New Jersey, I jumped as high as I possibly could…considering I was on a train. I fully expected to land at least a foot or so away from the spot where I originally stood. Not so. I landed in exactly the same spot as where I stood prior to jumping.
Several years ago, I tried this same thing on a Lufthansa 747-400 somewhere over the Atlantic and got the same results. Someone told me that the reason for this was that the plane is pressurized. I’m certain that trains are not pressurized, so why did this happen? If you’re standing on a moving platform and jump, shouldn’t you NOT land in the same spot that you started out from?
You have to remember that you’re moving the same speed the plane/train, so you’ll move just as much as it while you’re in the air as when you’re grounded. The amount you decelerate in that short of time is pretty negligible, hence, you land in the same spot.
No. You are moving exactly the same speed as the train (or plane). Therefore you move forward while you are in the air the same distance the train or plane does.
It would be a bit different if you were outside the vehicle, since air resistance would have an effect on you, and push you back. But on a space craft, there would be no effect, and you would come down in the same place.
Why would you expect to land further back than you took off? Say the train is moving at 100mph. As long as you are standing on the floor you are also moving at 100mph.
Newton’s First Law of Motion states that "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. "
So, you are travelling forward at 100mph, as is the air in the train (you don’t feel a 100mph wind in your face, unless you stick your head out of the window (in which case beware of tunnels!)). You jump upwards, which will have no effect on your forwards motion, as it is perpendicular to it. So, relative to the ground outside the train, you are actually jumping in an arc forwards, travelling at the same speed as the train. Thus, when you land, the spot of floor from which you took off is still right under your feet.
Of course, if the train accelerated or decelerated rapidly while you were in the air, then you would land behind or in front of where you took off (or faceplant the wall of the carriage…)
Next time, try doing it when the train is rounding a corner. In that case, you’ll move in a straight line, while the car moves in a curve, and you will probably bump into the seats beside the aisle. (Actually, don’t try that. With my luck, you’d sprain your ankle and sue me for suggesting it.)
The principle of relativity says that if you are in uniform motion (travelling in one direction at a steady speed), there is no test you can do that will prove you are moving. After all, the train could just as easily be standing still, with the landscape racing away toward the caboose.
Okay, lets alter the experiment a bit. Say you are on a flatbed car of the train or on top of the train. My WAG would be that the air resistance would slow you down some, but you’d have to stay airborne a little while to get any good distance out of it.
Not that I’m hoping that someone will try this.
Now that I think about it, I’ve seen stuntmen do this in movies, leaping from one car to another going forward. Do you have to jump harder to go forward than you would to jump to a car towards the rear of the train? Or does that short time in the air not really affect your momentum?
Another analogy: The Earth is constantly spinning at a great speed. I you are standing outside and jump in the air, you land in the same place, because you are moving at the same speed as the surface of the Earth. This is something we just take for granted, but its the same principle inside a constantly moving train.
If the plane is maintaining “constant acceleration” then yes you would land slighter behind yourself. If the plane is maintaining constant speed then you would land in the same spot.
If the plane is actually accelerating then yes, you will land further back.
If, however, you mean “The plane is using its engines to maintain speed, but you are not being powered so you should land further back” then no - the plane has to use its engines just to keep a constant speed, as it has to overcome air resistance. Inside the plane, you don’t have any air resistance to worry about (at least not in a forwards-backwards direction) so you will maintain a constant velocity forwards.
Yes; assuming that it is a calm day (no strong wind currents) and the train is moving at 50mph then it will be like trying to run headlong into a 50mph wind (not easy); running toward the back of the train will be like running with a 50mph wind at your back; it will be difficult to stop.
Remember that a person standing on the ground watching you jump on the train will see you move in a parabola, it all has to do with your frame of reference.
The planet earth, along with the sun and the rest of the solar system, is spinning around the center of the galaxy at something akin to 600,000 miles per hour IIRC. Rather than wonder why the train didn’t move out from under you when you jumped up, you should wonder why you didn’t smash into the walls of the train at 600,000 mph as the entire solar system started to rush on without you while you were in mid-air. It’s the same answer.
Time slows down on the airplane as observed by someone on the ground. An observer on the airplane would say that the “stationary” clock was running more slowly. (How does your brain feel now?)
