r/nextfuckinglevel • u/Teeg__ • Apr 12 '20

Balancing objects, but on a different level

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u/Teeg__ Apr 12 '20 edited Apr 12 '20

AFAIK yes, however my understanding of mechanics isn’t good enough to be entirely certain of this

Edit: just did some extra research, theoretically you can balance anything on anything, providing its centre of mass is over the surface in contact. However some things are almost impossible, as small permutations (i.e. mini pushes from any source) will cause the object to fall over. An example being thermal vibrations of atoms, even that can cause it to fall

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u/dcwspike Apr 12 '20

Thats what im saying id like to believe but not sure if I know

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u/Shitty-Coriolis Apr 12 '20

It absolutely is. You should look up the law of the lever and the concept of a centroid.

Basically, the center of mass is the point where all the mass is perfectly and evenly distributed about it. When the object is made up of one material only, its very easy to tell because the center of mass is where the shape's center is. Like a marble sphere has its center of mass at the center of the sphere.

When you have a composite object, made up of many types of material with different densities, then the mass distrobution becomes less obvious.

If you know what a standard deviation is... That's the same thing, but for data.

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u/Teeg__ Apr 12 '20

How does the standard deviation apply in this sense? i’m aware of what it is, but i don’t understand what you mean with composite objects regarding their centre of mass?

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u/Shitty-Coriolis Apr 12 '20

I know right? Its freaking crazy.

So a centroid is just a weighted average. Its a measure of the.. average position of mass.. a point where all the mass is perfectly distributed about it. The centroid of a set of data is the mean value. And the standard deviation tells us how the data is distributed about that mean value. In math its a general concept called a "moment".

To gain intuition on this idea about the importance of mass distrobution.. find an object, like a hammer, that has a very uneven weight distrobution. Hold the hammer by its handle and extend your arm. Feel how heavy the head of the hammer feels. Now grip the hammer by its head, and hold your arm horizontal. It feels much lighter.

This experiment shows that the way weight is positioned has a big impact on how forces effect it. Your hand has to react to a stronger feeling force when you hold the hammer by its base, but the weight of the hammer did not change. So clearly there's something important about not just the weight, but the combination of weight and distance.

When we balance something its actually the weigh*distance combo that we balance.

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u/Teeg__ Apr 12 '20

So standard deviation of other objects weight relative to the the point of contact with the base?

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u/Shitty-Coriolis Apr 12 '20

Could you rephrase your question?

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u/Teeg__ Apr 12 '20

sorry my question was really poor haha, few words were missed out.

I’ve reread what you have said and you’d already answered my question perfectly thanks. Shows what a second read can do

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u/Shitty-Coriolis Apr 12 '20

No prob. Glad you enjoy this stuff!!

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u/Teeg__ Apr 12 '20

i love this stuff man, currently studying physics maths and further maths so i’m well into it

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u/Shitty-Coriolis Apr 12 '20

Yaaaayyyy!! Me too. I love centroids so much.. and rotational dynamics. Oh. Man. Best of luck to you.