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Jerk in Elevator

02/16/2014 2:12 AM

When an elevator running at constant speed of 2mps makes an emergency stop due to power failure, there is a sharp rate of deceleration due to mechanical braking system. The deceleration continues for about 2 seconds before the elevator makes a dead stop. The worst jerk perceived in the lift cabin during the deceleration phase is just before the end of the travel when the elevator comes to an halt.

Why is the jerk highest at the end of travel?

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#1

Re: Jerk in elevator

02/16/2014 3:39 AM

The guy at the end of the hangman's noose asked the same question, " why the sudden jerk at the end of the rope?

The answer to your question is, (d) all the above. And be glad it stopped!

Whats your next test question? You have a 25% chance of guessing the correct answer in a multiple choice question, a,b,c or d. And your odds get better if you only have a,b or c to choose from.

In other words, we do not do school homework, especially for someone at the end of their rope.

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#7
In reply to #1

Re: Jerk in elevator

02/17/2014 1:26 AM

Often the JERK will appear in the most expected places. I am certain YOU would agree!

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#2

Re: Jerk in elevator

02/16/2014 4:54 AM

You may notice the same thing when driving a car, unless you lift up about halfway on the brake just as the car as about to finish stopping.

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#10
In reply to #2

Re: Jerk in elevator

02/17/2014 6:46 AM

Yup - totally agree with Tornado. If you can find out why you keep travelling when you leave your foot hard on the brake pedal of a car you have solved your lift problem. A good driver who cares for his/her passengers always lifts off!

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#3

Re: Jerk in elevator

02/16/2014 10:30 AM

Sorry, I cant help myself.

Who was the jerk in the elevator that pressed the Emergency Stop button?

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#4

Re: Jerk in Elevator

02/16/2014 11:40 PM

I guess it's true when they say "It's not the fall that will bother you but the quick stop at the end!"

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#5

Re: Jerk in Elevator

02/16/2014 11:57 PM

If I encounter a jerk in the elevator I ignore him as best I can and get off at the next floor. Just a woman's perspective...

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#6

Re: Jerk in Elevator

02/17/2014 12:52 AM

So on the assumption it is school work, ask yourself:

(a) is the deceleration level really any higher? and

(b) is it really all about perception and (c) what is it that is being perceived exactly?.

If you answer that those questions you'll probably twig to the answer.

Hint - there is nothing on this planet that is not "elastic" or which does not deform under load (that I can think of until maybe you get to the quantum level!)

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#8

Re: Jerk in Elevator

02/17/2014 2:52 AM

Kinetic NRG causes this.

Although.....I heard that if you jump up 'just before' the elevator reaches it's absolute stop it will save you from feeling the jerk.

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#9

Re: Jerk in Elevator

02/17/2014 4:36 AM

That has to be the best and most misleading title ever on CR4, I loved it!!!

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#14
In reply to #9

Re: Jerk in Elevator

02/18/2014 7:14 PM

I rode in an elevator with a jerk.

He passed some body gas... a lot... inside the elevator cab...

That was just wrong on so many levels.

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#15
In reply to #14

Re: Jerk in Elevator

02/19/2014 5:31 AM

PHEW!!!!

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#17
In reply to #14

Re: Jerk in Elevator

02/22/2014 8:07 PM

That answer stinks.

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#11

Re: Jerk in Elevator

02/17/2014 7:56 AM

The jerk is the rate of change of deceleration. When the elevator stops, deceleration ceases, and it is this rate of change that you experience because your body is flexible.

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#12

Re: Jerk in Elevator

02/17/2014 8:32 AM

...i.e. where s is position and t is time:

d3s/dt3= infinity

Just make it smaller and everything will be fine.

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#13

Re: Jerk in Elevator

02/17/2014 3:01 PM

It has to do with the position of the counter weight....when the elevator is at the lower floors, the weight alone is enough to lift the elevator, therefore the brake is slowing the descent of the counter weight...when the elevator is near the top the weight is hanging below the lift and exerts more stress on the lines....When the elevator is about half loaded, the effects should equal out...

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#18
In reply to #13

Re: Jerk in Elevator

02/22/2014 8:08 PM

What about when the jerk in the elevator is half loaded?

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#16

Re: Jerk in Elevator

02/20/2014 3:26 AM

Use hydraulic breaking thruster to eliminate jerk during breaking action.

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