Perhaps it’s just my imagination but I always find it seems more tiring to walk up a moving escalator than a normal set of steps. I’m wondering if the motion of the steps causes some sort of momentum change or something else.
So do I expend more energy walking up, say 20, upward moving steps than it would be to ascend 20 identical but motionless steps?
I suspect the rise of a moving escalator is higher than the rise of an average staircase, which would no doubt account for the extra effort required.
Just my WAG!
At the beginning and end of the escalator, the rise between the steps is of differing heights, and this has long been known to be disorienting to someone ascending a set of stairs. I don’t think you expend more energy, but your balance is more disoriented, which may feel similar.
Ah but the wording of my question firstly discounts the idea that a fixed staircase is of a different size - although that may account for my feeling of effort. My question also discounts the expanding steps at the top and bottom of the escalator - rather I’m interesting in whether the momentum of the staircase affects the effort one has to put in to walking up it.
The short answer to your question is no. The work you do is the difference between the work if you stand on one step and let the escalator move you, which is zero, and the the work you do if climbing the steps. This difference is the same work you would do if the escalator were stationary.
This same principle is what allows people to easily move faster on “people movers” at airports, just level instead of up a hill.
Any perceived difference is either psychological, or you are not performing the comparison as rigorously as what you stated in your question. Find a stationary escalator and climb up the steps. You may find it takes more energy that you expected. I think sandra nz is onto something there.
Steps on an escalator certainly are higher than fixed stairs. The escalator at my local bus station broke down the other day and I elected to walk up instead of queuing for the lift. I was half way up before I decided that waiting might have been the better option.
Its your imagination.
Imagine you are on an airplane doing 700km/h, and the nose is tilted up a bit… well its just gentle tilt. You are at the back and walk up to the front ? Are you overwhelmed by the effect of 700 km/h ? No not a all.
So what is the difference between the aeroplane and the escalator ? None at all.
My point is that if the aeroplane situation didn’t create “extra work” to climb the slope, the escalator won’t either.
Also, Escalators create more work to climb by each step clunking around under your foot…There’s energy wasted in making it wobble around… making the rubber band hot and wearing out the track a little.
Aren’t both the rise of escalator steps and the, well, depth (the distance from the front lip of a step to the rearmost) greater than that of a standard stairway? I think that would account for more work (distance X weight) being necessary to climb an escalator. Once you’re on the escalator and moving, your initial surge of acceleration is over and should no effect.
Instead of comparing walking up an escalator to a standard stairway, I’d suggest comparing walking up an operating escalator to a stopped escalator. That would eliminate the differences in tread rise and depth and just allow you to compare effort with to without motion.
Strictly speaking, you might get some difference from air resistance. But that’s going to be small at walking speeds (even walking augmented by escalator motion), and the air is probably moving with the escalator to some degree anyway.
You would expend more effort stepping onto the first, moving step, because you have to accelerate yourself to the speed of the escalator. You also expend more effort decelerating when you step off the escalator. Once you are on the escalator, and moving at the same speed as it, the effort of walking up the stairs is the same as walking up a set of stationery stairs of the same height.
Regards,
Shodan
It seems to me that you can shed some light on this problem by considering how difficult it is to walk up an escalator which is [A] moving up, ** not moving, or [C] moving down. Can we all agree that walking up the down escalator is more work than walking up a stationary one? They “why” may be tricky to answer; perhaps it’s because your feet have to push against the step you are leaving in order to reach the next step and the step you’re leaving is moving away from you therefore it’s more difficult to push against it. But regardless of the “why”, if we agree that C>B then it seems wrong to me to claim that A=B. It seems more logical to me that C>B>A and the faster the speed of the escalator the more unequal it becomes.
Yes, that’s right, I’m claiming that it is EASIER to walk up an escalator which is moving up. It has the illusion of being harder because you expending energy at a faster rate, but the total amount of energy being expended is slightly less.
Consider a stationary escalator with 20 steps from bottom to top. You have a mass of 70 kg and each step is 30 cm, total height 6 meters. Lifting your 70 kg mass up 6 m requires just over 4000 Joules of energy. If you do it in 10 seconds, that’s 400 Watts of power. If you do it in 5 seconds, that’s 800 Watts (Joules per second). So, yeah, 800 Watts feels harder but you’re doing it in a shorter time. So output is the same.
But if the steps are moving down, you have to push harder on each step, which is more difficult, and if they are moving up, it’s less difficult. I just don’t know how to quantify it.
But will the people be able to achieve lift-off?
(ba-dum-tshhh)
If you start walking up the steps as you transition from the horizontal part to the upward-travelling part, you’ll feel stepping to be more difficult, because you are being accelerated upward during this transition.
Once you get past that point and you are travelling in a straight line, it makes no difference.
If you start walking near the top, where the transition from going up goes back to horizontal, you may find yourself feeling a little light-footed.
No, we cannot. It’s exactly the same amount of work per step.
It takes more steps.
Ninja’ed!
The number of steps you need to go from the bottom to the top of a moving up escalator is obviously fewer than the number of steps on a stationary one of equal rise. The number of steps you need to go from the bottom to the top of a moving down escalator is obviously more than the number of steps on a stationary one of equal rise.
Is there any difference between the work done on a single step? There shouldn’t be, any more than there would be a problem throwing a ball inside a moving railroad car. The movement affects the entire system equally.
It’s all perception.
The nice thing about an escalator is that is can never break down.
It IS more work, for a couple of reasons:[ol]
[li]You’re trying to accelerate your vertical and horizontal movement on top of what the escalator is already providing. The effort need to accelerate to a given speed is exponential rather than linear (i.e. increasing speed by 20% takes more than 2x the energy to increase speed by 10%).[/li][li]When you’re traveling up a normal stairway, your forward momentum reduces the load on your trailing leg. On an escalator, that trailing leg still has to carry the load of keeping your body moving at the escalators speed. [/li][/ol]
A couldn’t find a cite in my quick search, but I’m sure somebody more knowledgeable in physics can provide the basic formula that proves this (acceleration against a constant force (i.e. gravity, drag)).
The maximum force produced by a human leg varies depending on the angles of your joints. This is why it’s important to adjust your bicycle seat properly. You want your legs to stay within the range of angles where your muscles work efficiently. Cite.
Risers are further apart on escalators than they are on stairs. You’re doing the same amount of total work to raise yourself up to the next floor. But doing do requires you to extend your leg muscles outside the range of angles where they can push effectively, so it feels harder.
Ah, but the only force you put into walking up an escalator should be about the same per step as walking up it when it’s not moving. The escalator is providing the power if you just ride it up. Anyway, since you’re going up anyway plus climbing up, the amount of steps taken will be fewer, so I conclude walking up an upward moving escalator will require less human energy than climbing the same escalator when it’s stationary.