What happens in the experiment:
Two forks seemingly magically balance on the rim of the cup, with the support of a mere toothpick.
Watch the video
Here is a video of an experiment I did (see it on youtube).
How it works:
This is due to the law of centre of gravity.
This law states that every objects has a point, where all gravity will effectively act. This is the midpoint of all the mass in the object. In a simple shaped structure such as a cube, this will just be in the middle, as there is an equal amount of mass in all directions of that point.
However, in the complicated, but symmetrical structure of two forks wedged together, the centre of gravity will act somewhere in the air (that is why two forks dip inwards if you hold them by the prongs)! I know this is complicated to understand, but the rest of the object does not affect the gravitational pull. If you piled up ten more forks, equally on both sides, the structure would still balance (if you had a really strong toothpick!).
Some people may use the term 'centre of mass' as well. On earth we can use these terms interchangeably, however in different gravitational fields, there is a difference.
If you are confused about the difference between centre of mass and centre of gravity, don't worry, as I will go over this in a later post, if you can't wait till then, click here.
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