Explanation to some observations

[zorro]

I need explanations of some observations -

1) How do they remove the anti-theft tags from clothes (mechanism behind it)?
2) How do trolleys no matter how heavy stick to a cartveyor?
3) Why do we need to apply more force to close the door (not throughout - just before complete closing) of a room in which there is an exhaust-fan (bathrooms usually)?

 

[zorro]

Someone please answer atleast one.

 

[Drakkith]

I'm not sure of the 1st one, and I don't even know what the 2nd one is.

As for the 3rd, if the door closes from the inside, then you are pulling the door closes against a force of air trying to get in and out through the fan. My bedroom door will close itself when my AC unit is on in my house, as the air wants to get out of the door and will force it closed in the process.

 

[zorro]

I'm not sure of the 1st one, and I don't even know what the 2nd one is.

In hypermarkets (like Carrefour) that have different floors for shopping, there are cartveyors (analogous to escalators) to help move from one floor to another with heavy trolleys. You don't need to apply any force to hold these trolleys, they 'stick' to the cartveyor.

As for the 3rd, if the door closes from the inside, then you are pulling the door closes against a force of air trying to get in and out through the fan. My bedroom door will close itself when my AC unit is on in my house, as the air wants to get out of the door and will force it closed in the process.

The problem here is that you don't apply a constant force to close the door. You have to apply much more force just before closing. You will understand it clearly if you try it out.

 

[Drakkith]

The problem here is that you don't apply a constant force to close the door. You have to apply much more force just before closing. You will understand it clearly if you try it out.

Sorry, my two examples were opposites. Does your door open to the inside of the room or the outside?

 

[zorro]

Does your door open to the inside of the room or the outside?

Haha ...It opens to the inside of the room. Is that relevant?

 

[Drakkith]

Haha ...It opens to the inside of the room. Is that relevant?

If the fan is on, then you have to close the door against air pressure. It only has an effect right before the door closes. I'm guessing that's why it's hard to close.