I was once asked to find a way to find the centre of gravity of a coke bottle. As soon as I started mentioning string, ruler etc., the interviewer told me I have nothing else, only the coke bottle..

Pinch it with your fingers? It's a test to make sure you don't die of boredom in meetings.

I choose option ö: I snort the coke and use my drug-fueled inspiration to invent a new JS framework 😬

You can do that with hands. Put your one finger on one end and other finger on other end. Slowly, very slowly, start sliding them towards each other. The line where they meet is the plane of centre of gravity. There's a good reason behind this, you can find on YouTube.

@retard if you get them towards each other isnt the point they meet the halfpoint?

@hubiruchi If the center of gravity is nearer to your right finger than to to the left finger more mass will push down on that finger, increasing the friction you have to overcome to move the finger, meaning your left finger will move faster than the right finger.
At least that is how I would guess it works.

@retard "the line is the plane".
Something feels terribly wrong here

@hubiruchi nope.. they adjust by themselves. If one finger is far away from centre of gravity than other finger then it'll automatically stop moving. I'm not so good at physics that's why I recommend you to look at sources for complete explanation

The interesting part is: wouldn't bottle made out of coke just... Spill?

@stacked the line is not plane. I'm talking about the plane where those two fingers will meet (a line on that plane)

Spinning the bottle would show you the center of gravity