roolit
Newbie level 4
I came across this interesting experiment but I couldnt follow some part in the end.. Can anyone explain?
" Imagine you have a box filled with several glass marbles. Now you give the box a good shake and place it on a table. When opening the box now, where would you expect to find the marbles? Well, our everyday experience tells us, they will be on the bottom of the box.
Now imagine we use the same box but replace the glass marbles by tiny ones with a diameter of several micrometer (the thousandth part of a millimetre). Now we close the box again and give it a good shake. When opening the box now, where would you expect to find the marbles?
On the bottom again?
This is where our macro-world experience mislead us. The marbles would be equally distributed on each surface of the inside of the box, sticking to bottom, side-walls and the lid. This is due to the fact that when reducing the size of a body to micro-dimensions the gravitational force becomes more and more unimportant compared to other forces acting on the body.
More specific, the gravitational force being a volumetric force scales with L3, whereas surface forces like the electrostatic force scale with L2. This means when reducing the dimensions of a body by a factor of 1000, the gravitational force is reduced by a factor of 1000-3 = 10-9 whereas the electrostatic force is reduced by 10-6.
Therefore, the weight of a body can be neglected in almost all instances when dealing with MEMS devices, except in special devices such as accelerometers."
My doubt is.. why is there an equal distribution of the micro-marbles? I understood that, gravity will have not an effect at that scale but i didn't follow why there should be an equal distribution of the marbles inside the bottle... Thanks for your help in advance?
" Imagine you have a box filled with several glass marbles. Now you give the box a good shake and place it on a table. When opening the box now, where would you expect to find the marbles? Well, our everyday experience tells us, they will be on the bottom of the box.
Now imagine we use the same box but replace the glass marbles by tiny ones with a diameter of several micrometer (the thousandth part of a millimetre). Now we close the box again and give it a good shake. When opening the box now, where would you expect to find the marbles?
On the bottom again?
This is where our macro-world experience mislead us. The marbles would be equally distributed on each surface of the inside of the box, sticking to bottom, side-walls and the lid. This is due to the fact that when reducing the size of a body to micro-dimensions the gravitational force becomes more and more unimportant compared to other forces acting on the body.
More specific, the gravitational force being a volumetric force scales with L3, whereas surface forces like the electrostatic force scale with L2. This means when reducing the dimensions of a body by a factor of 1000, the gravitational force is reduced by a factor of 1000-3 = 10-9 whereas the electrostatic force is reduced by 10-6.
Therefore, the weight of a body can be neglected in almost all instances when dealing with MEMS devices, except in special devices such as accelerometers."
My doubt is.. why is there an equal distribution of the micro-marbles? I understood that, gravity will have not an effect at that scale but i didn't follow why there should be an equal distribution of the marbles inside the bottle... Thanks for your help in advance?