physics question, I think

jon f mn · Jan 29, 2014

Why does my coffee cup always rotate clock wise when sitting in the cup holder. I alwas set it down with the handle at about the 3:00 position and it always turns to the left to the 11:00 position where the handle hits the dash. Never counter clockwise to the 1:00 position where it would hit the dash. If the truck tilted to the front it would go counter clockwise, tilted to the left it would stop at the 9:00 position. This is distracting me while driving today so a quick response will be safer for the other drivers out there. lol

in-too-deep · Jan 29, 2014

I bet if you were south of the equator, it would go the other way.

Ted in NE-OH · Jan 29, 2014

Just like water runs down the drain.

Janicholson · Jan 29, 2014

The vibration in the truck is ransmitted to the holder. Take an ink pin and hold the point still while puting your Fingers in a "OK" ring about 2/3 of the way up. ROtate you "OK" sign and the pin will rotate . Jim

jm. · Jan 29, 2014

Well first of all be careful and do not have a wreck worring about this real important problem but let me say all three answers have hit it right on, kinda like the way God designed things or something like that.

Anonymous-0 · Jan 29, 2014

That old truck engine is rotating that way. You could run the engine CC wise and the vibration would rotate the cup the other direction, but the thing wouldn't have many forward gears.

rrlund · Jan 29, 2014

Same reason the water spins the way it does when you flush the toilet. Would probably spin the other way if you were in the southern hemisphere.

LA in WI · Jan 29, 2014

Jon,
Simple. You have a right-handed cup.
Get a left-handed cup if you want it to go the other way.
Or buy one with no handle.
If that doesn't work, buy one with no bottom.
LA in WI

Geo-TH,In · Jan 29, 2014

If you had a 2 handled cup, it wouldn't rotate.

glennster · Jan 29, 2014

in a nutshell
poke here

J.Wondergem · Jan 29, 2014

The only think I can come up with, if it wont turn left, it's not a racing cup.

Mike (WA) · Jan 29, 2014

I was going to post about the Coriolis Force as well, and first looked it up in my Websters- they described it as "a fictional force. . ."

My physics prof would not have been very happy about THAT-

As for your cup, my mother had a general scientific principle that she would have immediately invoked in this case- the Perversity of Inanimate Objects- which was pretty much a catch-all for everything that could not be otherwise explained.

DENNIS MIN · Jan 29, 2014

jon of mn,

You must be OLD! LOL. Only old folks know which way a clock turns, LCD,LED and all. Let's get rid of reading. writing , arithmetic while we are at it.

Meant light-hearted of course.

D.

Whichester1 · Jan 29, 2014

in-too-deep has it correct. Experienced it while living in Southern Africa.

Anonymous-0 · Jan 29, 2014

Cup is not balanced, the handle vibrates with acceleration, and the fact that there is weight on the drivers side (I speak from experience, here!). if you had a passenger, things would balance out! Pick up a lot lizard, and see if the cup still rotates!

Chuck (CA) · Jan 29, 2014

What happens when you drive in reverse?

jon f mn · Jan 29, 2014

If I got one with no handle wouldn't it continually rotate? Thereby making the coffee dizzy? And if I drink dizzy coffee would it then make me dizzier too? That could be dangerous. And a cup with no bottom, well no coffee makes Jon a crabby boy, nuf said on that I think. lol

jon f mn · Jan 29, 2014

Never checked that. I'll watch tomorrow.

wolfman · Jan 29, 2014

It is due to the Earth's rotation on its axis. Like when you flush the john the water swirls right. If you were in the southern hemisphere, the cup would rotate the other direction. We likely don't notice it, but due to the Earth's rotation on its axis, we're traveling about 1000 mph. Hence the saying: Stop the world and I'll get off. If it suddenly stopped, you'd be in orbit. I think it's about 10,000 mph due to Earth's revolving about the sun.

Janicholson · Jan 29, 2014

New Demo!!
Take two Orings, one of which is just small enough to fit inside the other with a bit of space around it (not a lot!)
Mark the inner ring with a dot of whiteout or other visible mark.
With them on a flat surface, move the outer ring in a small circle (do not rotate the ring, oscillate it so it scoots in a small circle.
The inner ring will actually rotate! (opposite of the oscillation direction!)
The direction depends on the harmonics of your engine and the mounting of the holder. In a different location, it might rotate the other direction. Move the outer ring in an oscillation the other direction and it will rotate the inner ring the other direction.
An added ounce of very soft rubber on the outside of the holder (that could absorb the vibration) might stop it!
As would a notch in the holder, and a "key" glued to the cup. It is not Coriolis effect! Jim

James Williams · Jan 29, 2014

Does the water in a comode rotate different direction upstairs than down stairs,I was told it did but I dont know

jimmy

RalphWD45 · Jan 30, 2014

Jon, if you were down in Atlanta, you would have plenty of time to ponder the question, while sitting crossways of the free way, waiting to be allowed to try and move. I was relived to see your post, and know you weren't down that way.

wolfman · Jan 30, 2014

Different in northern hemisphere vs southern.

physics question, I think

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