Physics Question

[LakeSuperior]

Technically, taking one step on the escalator requires less energy than taking the same step on a fixed stairway.

The difference is the net change in the gravitation force is greater when taking one step on the escalator.

Your net vertical change is greater on the escalator while taking the step making the force of gravity progressively a little less during each instant that you are taking the step.

[conachair]

Originally Posted by LakeSuperior

Technically, taking one step on the escalator requires less energy than taking the same step on a fixed stairway.

The difference is the net change in the gravitation force is greater when taking one step on the escalator.

Your net vertical change is greater on the escalator while taking the step making the force of gravity progressively a little less during each instant that you are taking the step.

Would the increase in air resistance more than mask this?

[sailorchic34]

Originally Posted by LakeSuperior

Technically, taking one step on the escalator requires less energy than taking the same step on a fixed stairway.

The difference is the net change in the gravitation force is greater when taking one step on the escalator.

Your net vertical change is greater on the escalator while taking the step making the force of gravity progressively a little less during each instant that you are taking the step.

So the net change in weight of a 200 pound man rising one foot would be something around 0.000018 pounds. there is also an increase in weight caused by the slight decrease in air pressure of roughly 0.000001 pounds.
We could also add in light pressure and magnetic effects on the iron in the body. But all that combined is not really measurable as it's below the noise level in any load cell and makes no appreciable difference in the amount of work done.

[jwcolby54]

OK so I am going to say that you have to get up the same distance. However... you have to take fewer steps to do that because every step the escalator is moving you up at the same time.

So less energy by a fair amount.

Unless you were walking up the down escalator...

[Stu Jackson]

Originally Posted by jwcolby54

1 OK so I am going to say that you have to get up the same distance. However... you have to take fewer steps to do that because every step the escalator is moving you up at the same time.



2 Unless you were walking up the down escalator...

1 But that wasn't the question.

2 Great!

[jkindredpdx]

Thanks all... (and yes I could have googled it, but I trust y'all so much more)

So If I'm in a rocket blasting off (a few feet from the surface) of the earth I would use no more energy than climbing a ladder while the rocket was sitting on the launch pad?

[jkindredpdx]

Originally Posted by Claude_Marie

When you arrive at the top of the escalator, may I call it last step.
The acceleration provided by the escalator + your first step "on firm ground" when you generate your own acceleration add on, don't they ?

just like a boat with its own acceleration + acceleration due to swell = surf.

I would assume first step (acceleration) and last step (deceleration) would offset each other somewhat...

I was asking about energy per step during the time that my body is moving at the same speed as the escallator.

[sailorchic34]

Originally Posted by jkindredpdx

Thanks all... (and yes I could have googled it, but I trust y'all so much more)

So If I'm in a rocket blasting off (a few feet from the surface) of the earth I would use no more energy than climbing a ladder while the rocket was sitting on the launch pad?

Only if your from The Duchy of Grand Fenwick. For everyone else the rocket is under acceleration so going up a ladder in a rocket under acceleration would use more energy then going up the ladder with the rocket at rest.

[jkindredpdx]

Originally Posted by jwcolby54

OK so I am going to say that you have to get up the same distance. However... you have to take fewer steps to do that because every step the escalator is moving you up at the same time.

So less energy by a fair amount.

Unless you were walking up the down escalator...

Up the down escalator would be less energy "per step" because I'm not climbing (lifting my body).

[sailorchic34]

Originally Posted by jkindredpdx

Up the down escalator would be less energy "per step" because I'm not climbing (lifting my body).

Nope, your still lifting the body and using the same amount of energy, as both you and the escalator are on the same frame of reference.

[jkishel]

The work required to raise a weight, w a vertical distance h is wh.

When a person with weight w climbs a flight of stairs with vertical distance h, the person produces wh of work (neglecting the very small amount of work needed to move the person horizontally).

When the same person stands stationary on an escalator and is raised h, the same amount of work is expended, wh, but entirely by the escalator.

When the same person climbs steps on the moving escalator, the same amount of work is expended, wh, some by the person and the rest by the escalator, again neglecting the negligible work expended in the horizontal direction.

The escalator reduces the amount of work required by a person to climb a flight of stairs, down to zero if the person just stands stationary on the escalator. That's why we have escalators.

[skipmac]

Originally Posted by Caribbeachbum

Only for the step on and the step off. The escalator moves at a constant rate, so delta-v exists only at those two points. Walking up the escalator is no different than walking up stairs.

I do believe this is correct. More energy for the first step as your body has to accelerate to the speed of the escalator. Less however for the last step since you will be decelerating. In the middle your body and the escalator will be in the same frame of reference IE both moving at the same speed so the energy expended step to step should be more or less the same as energy expended walking up fixed stairs.

Originally Posted by Caribbeachbum

But if you add in the energy expended by the escalator system to maintain the constant rate against the forces applied when you walk up, then yes, walking does consume more energy than merely riding.

Don't think I agree with this. Work is defined by force and distance. In this case the same weight of your body is moved the same distance (assuming stairs and escalators are the same) so the total work done by the escalator + walking will be the same as the work done by walking alone up fixed stairs. Time nor speed change the amount of work done.

[jkindredpdx]

Originally Posted by sailorchic34

Nope, your still lifting the body and using the same amount of energy, as both you and the escalator are on the same frame of reference.

I believe you... it just seems that from the time I set my forward foot down and start lifting my body, the step moves toward me. Color me

[skipmac]

Originally Posted by jkishel

The work required to raise a weight, w a vertical distance h is wh.

When a person with weight w climbs a flight of stairs with vertical distance h, the person produces wh of work (neglecting the very small amount of work needed to move the person horizontally).

When the same person stands stationary on an escalator and is raised h, the same amount of work is expended, wh, but entirely by the escalator.

When the same person climbs steps on the moving escalator, the same amount of work is expended, wh, some by the person and the rest by the escalator, again neglecting the negligible work expended in the horizontal direction.

The escalator reduces the amount of work required by a person to climb a flight of stairs, down to zero if the person just stands stationary on the escalator. That's why we have escalators.

[jkindredpdx]

Sorry no the orignal question was "Energy per Step"