Solving Rotary Friction Problem at Ye Olde Swinging Door

[Ben2]

Homework Statement: A door opened at 75 degrees from the latch remains at rest. When moved to a position 60 degrees from the latch, it slowly closes on its own. Is there another possible cause besides a sloping floor?
Relevant Equations: \tau = r x F; v = \omega x r; a_T = \alpha x r, where all quantities are vectors.

I'm in a house with repurposed parts. I'd like those with physical intuition to look at a problem involving rotary friction. Thanks in advance!

 

[phinds]

The issue COULD be with the hinges. Have you tried oiling the hinges to see if that makes any difference?

 

[kuruman]

Argh! @phinds preempted me. I had this happen to me until I oiled the hinges.

 

[Ben2]

Good suggestion! I've often wondered if different radial sections of a hinge could experience different amounts of friction.

 

[kuruman]

There could be any combination of rust, dirt and moisture accumulating unevenly on the hinges.

 

[berkeman]

(thread moved from the Homework forums to the General Discussion forum)

 

[hutchphd]

Is the door hung so it will to close from gravity alone? Is this a design feature or just an old house?

 

[Bystander]

There could be any combination of rust, dirt and moisture accumulating unevenly on the hinges.

..., plus a dollop of shoddy/slipshod construction, and it's anybody's guess....

 

[jrmichler]

Houses settle. Unevenly. I once designed a beam so that a friend could remove a load bearing interior wall. When we forced the beam into place, it had the effect of straightening the second floor. Every door on the second floor jammed.

 

[hutchphd]

My house turns 83 this year. Is that an old house? I can't decide ( After all it is only a dozen years older than moi and I never looked better although I do sag a little.......)

 

[Hornbein]

Do you want the door to close or to not close?

 

[jbriggs444]

Is there another possible cause besides a sloping floor?

You mean a non-vertical hinge axis? Perhaps one inclined in the plane that is 75 degrees from the latch?

One does hope that the hinges are all colinear. Flexing the door as it goes through its motion would allow a place for potential energy to be deposited.

 

[phinds]

OP hasn't been seen since several days ago when he posted the question. Seems he doesn't really care.

 

[berkeman]

I thought I heard something: Sounded like a door hitting someone in the...

 

[phinds]

I thought I heard something: Sounded like a door hitting someone in the...