Why Don't We Land at the Other End When Jumping on a Train or Subway?

[rebeccayippie]

I'm wondering, how come when we jump on the train or subway, we don't land all the way at the other end? Is it because of physics?

 

[ZapperZ]

Well, how come you can jump up and down on Earth and not get left behind dangling in space, considering that in some reference frame, the Earth is moving extremely fast!

Zz.

 

[Drakkith]

When you are on a train, or anything moving for that matter, like a car or bus or airplane, you are ALSO moving with it. When you jump you don't fly to the back because you are moving just as fast as the train is.

 

[rebeccayippie]

is there anything to do with gravity and the forces between us and the subway?

 

[G01]

is there anything to do with gravity and the forces between us and the subway?

Gravity does not factor into the explanation of the above phenomena you asked about in your first post. Gravity pulls you back to the floor after you jump, but is not involved in the reason why you land in the same place relative to the floor of the train. See Drakith's post above.

 

[rebeccayippie]

oh okay, now that i read it again, it makes sense. is it a concept of physics though?

 

[ZapperZ]

oh okay, now that i read it again, it makes sense. is it a concept of physics though?

It is a concept called "inertial frame of reference".

Zz.

 

[rebeccayippie]

It is a concept called "inertial frame of reference".

Zz.

thanks, do you think you can explain how inertial frame of reference is related to landing on the same spot on the subway?

 

[JaredJames]

thanks, do you think you can explain how inertial frame of reference is related to landing on the same spot on the subway?

When you jump up, there is nothing to slow you down.

You and the air are traveling at the same speed as the train, so there's nothing to cause your motion to retard.

Think of Newtons laws of motion:

Every body remains in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force.

In this case, there are no unbalanced force acting on you when you jump to cause you to slow down (no air resistance). The train is a closed system where all forces are balanced. In the trains reference frame, you are at rest (and so is the train). In the Earths reference frame, you are in motion (and so is the train). Regardless of which frame you choose, the forces are all balanced and so without an outside force acting on either body (air resistance or the trains brakes when you jump), you both remain either at rest or in constant motion and so you land in the same spot.

You only slow down when you jump out of a train because the air isn't moving at the same speed as the train and so it resists your motion and causes your speed to slow.
This also applies if you jump when the train is accelerating / decelerating you won't land in the same spot. The forces within the system aren't balanced.

 

[rebeccayippie]

When you jump up, there is nothing to slow you down.

You and the air are traveling at the same speed as the train, so there's nothing to cause your motion to retard.

Think of Newtons laws of motion:


In this case, there are no unbalanced force acting on you when you jump to cause you to slow down (no air resistance). The train is a closed system where all forces are balanced. In the trains reference frame, you are at rest (and so is the train). In the Earths reference frame, you are in motion (and so is the train). Regardless of which frame you choose, the forces are all balanced and so without an outside force acting on either body (air resistance or the trains brakes when you jump), you both remain either at rest or in constant motion and so you land in the same spot.

You only slow down when you jump out of a train because the air isn't moving at the same speed as the train and so it resists your motion and causes your speed to slow.
This also applies if you jump when the train is accelerating / decelerating you won't land in the same spot. The forces within the system aren't balanced.

thank you SO much

 

[sophiecentaur]

I'm wondering, how come when we jump on the train or subway, we don't land all the way at the other end? Is it because of physics?

Your question is an interesting one because it shows just what problems people had in accepting the ideas of Galileo, Newton and all the other revolutionary thinkers of their time. They thought that things 'naturally' slow down and that they need to be constantly pushed in order to keep going. If you had a horse and cart as your model and no one had invented ball bearings yet then that would be a reasonable assumption. They even thought. later, that the human frame would not be able to withstand traveling on a railway train!
It was by looking up onto the heavens, seeing how the planets moved and then relating this to what you see down on Earth that Newton's Laws of motion were developed to explain both situations in common.
These new Laws explain pretty much all of the physical situations that we experience in everyday life.

Your hat still blows off if you stand up in an open sports car at speed!