Sealed accelerating elevator

In summary: The image is of an aircraft altimeter showing 920 feet altitude above mean sea level at a barometric pressure reading of 29.92 inches mercury.
  • #1
Jazzyrohan
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If a sealed elevator moving with a constant velocity in upward direction suddenly starts accelerating upwards with an acceleration "a" ,will all the air molecules inside the elevator also accelerate with the same acceleration?
 
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  • #2
Jazzyrohan said:
If a sealed elevator is accelerating upwards with an acceleration "a" ,will all the air molecules inside the elevator also accelerate with the same acceleration?
What do you think and why?
 
  • #3
phinds said:
What do you think and why?
A body in an accelerating frame has the same acceleration as that of the frame if it is in direct contact with the frame,right?
So I think the air molecules will not be moving with the same acceleration and someone in the elevator will feel the air accelerating in the opposite direction.
Am I right?
 
  • #4
Jazzyrohan said:
Am I right?
Remember the equivalence principle - this is similar to being in (for example) a decompression chamber at rest on the Earth's surface. If you are correct, in a decompression chamber there would be a downwards wind until the air pooled on the floor.
 
  • #5
Jazzyrohan said:
A body in an accelerating frame has the same acceleration as that of the frame if it is in direct contact with the frame,right?
So I think the air molecules will not be moving with the same acceleration and someone in the elevator will feel the air accelerating in the opposite direction.
Am I right?

Where is your elevator initially? In gravity-free space? Where is the someone in the elevator initially? What happens to someone in the elevator as it accelerates? If there were only one air molecule (or a million) in the elevator, what would happen to that? If there is enough air in the elevator for someone to breathe, how does that change things?
 
  • #6
PeroK said:
Where is your elevator initially? In gravity-free space? Where is the someone in the elevator initially? What happens to someone in the elevator as it accelerates? If there were only one air molecule (or a million) in the elevator, what would happen to that? If there is enough air in the elevator for someone to breathe, how does that change things?
The elevator is subject to gravitational force on earth.That someone is standing on the floor in the elevator.
 
  • #7
Jazzyrohan said:
The elevator is subject to gravitational force on earth.That someone is standing on the floor in the elevator.

Have you ever been in an elevator? Did it feel like the air was moving down?
 
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  • #8
Jazzyrohan said:
A body in an accelerating frame has the same acceleration as that of the frame if it is in direct contact with the frame,right?
So I think the air molecules will not be moving with the same acceleration and someone in the elevator will feel the air accelerating in the opposite direction.
Am I right?
I think there is a subtly that has been missed in the responses so far. Those responses are looking at the macro level and correctly pointing out that your idea (apparently) that the air would pool at the bottom of the elevator is a non-starter. BUT ... they are overlooking the fact that you are right at one level in that the air in a non-accelerating elevator car in space would distribute itself evenly whereas the air in an elevator car on the ground on Earth or accelerating at 1G in space, WOULD in fact have a differential of air pressure due to the acceleration. I don't know if human measurement devices exist that can tell the difference in air pressure over, say, 10 feet at 1G, but if they could it would be there.
 
  • #9
phinds said:
I think there is a subtly that has been missed in the responses so far.

Perhaps you missed this:

PeroK said:
If there were only one air molecule (or a million) in the elevator, what would happen to that? If there is enough air in the elevator for someone to breathe, how does that change things?
 
  • #10
PeroK said:
Perhaps you missed this:
Didn't miss it but missed the point (so effective missed it, yeah)
 
  • #11
This video demonstrates the action graphically. In the video, the acceleration is horizontal, thus eliminating the complication of Earth's gravity.

 
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  • #12
anorlunda said:
This video demonstrates the action graphically. In the video, the acceleration is horizontal, thus eliminating the complication of Earth's gravity.
I must admit, that "balloon goes the wrong way" thing is one where, even knowing how and why it works, something low down in my brain just goes "Nuh uh! Must be fake!" Even when I'm watching it in reality.
 
  • #13
phinds said:
I don't know if human measurement devices exist that can tell the difference in air pressure over, say, 10 feet at 1G

There is, and it does:
upload_2018-11-10_16-58-8.png


The image is of an aircraft altimeter showing 920 feet altitude above mean sea level at a barometric pressure reading of 29.92 inches mercury. The skinny hand is 10,000 feet per numbered division, the short hand is 1000 feet per division (10,000 feet per revolution), and the large hand is 100 feet per division (1000 feet per revolution). The little tick marks are 20 feet apart.

You could also use an ordinary barometer. One thousand feet of altitude change is one inch of mercury pressure change, so 10 feet is 0.01 inch mercury. A good barometer should show that if you tap it lightly.

Or you can calculate the rate of change of pressure with altitude. It's the same rho*g*h calculation used for liquids. Rho for air is about 0.0765 lbs/cubic foot at standard temperature and pressure.
 

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What is a sealed accelerating elevator?

A sealed accelerating elevator is an elevator that is completely enclosed and moves at a constant acceleration, typically upwards. It is designed to reduce the amount of air resistance and improve energy efficiency.

How does a sealed accelerating elevator work?

A sealed accelerating elevator works by using a system of pulleys and counterweights to move the elevator car. The motor applies a constant force to the elevator, causing it to accelerate upwards. The sealed enclosure helps to reduce the effects of air resistance, allowing for faster and more efficient movement.

What are the benefits of a sealed accelerating elevator?

One of the main benefits of a sealed accelerating elevator is its energy efficiency. By reducing air resistance, it requires less energy to move the elevator car, resulting in lower energy costs. Additionally, the sealed enclosure also provides a quieter and smoother ride for passengers.

Are there any safety concerns with sealed accelerating elevators?

Like any elevator, safety is a top priority. Sealed accelerating elevators are designed and tested to meet strict safety standards. They also have multiple safety features, such as emergency brakes and sensors, to ensure the safety of passengers.

Can sealed accelerating elevators be installed in any building?

In theory, yes. However, the installation of a sealed accelerating elevator may require significant modifications to the building's structure and may not be feasible for older buildings. It is best to consult with a professional to determine if a sealed accelerating elevator is a viable option for a specific building.

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