Explanation

B) Good work! But why is this piece of paper so stable?

The platform composes itself from plenty structures which are causing a great stability.

The first structure is the folded paper between the bottom and the top of the platform. Try to see this structure like that: multiple stripes, comparable with rulers, which are sticked together. When you try to bend a ruler so that the flat side are on top and bottom, as follows it has only a height of one or two millimeters, you don´t have to use much force. But if you turn it, that the slim edges aree on top and bottom it is impossible to bend it. You find a justification looking at the moment of resistance. The moment of resistance describes the resistance an object opposes when a tension is exeted on it.

 

W=b x h2 / 6

W = moment of resistance

b = width of cross-section of the object

h = height of cross-section of the object

(Equation only for rectangular cross-sections)

 

The height is squared, the width is only added once. The rulers, continuing with this example, in our platform can not bend lateral, because they are sticked together. Staying nearly vertically their height is large and this causes a high stability.

For the legs of the platform the height is not important. You can discover this looking at the equation:

 

W=(ϖ/32) x ((D4 - d4)/D)

D = outer diameter

d = inner diameter

 

The height is not added in the equation.

Hollow pipes are nearly as stable as full-section pipes. That has multiple reasons:

Full-section pipes are much more heavy than hollow pipes. The full-section pipes are already strained by by their own weight.

The hollow pipes are not as stable as the full-section pipes which means that their moment of resistance is lower. The reason for this can be found in the equation: the outer diameter gets substracted with the inner diameter. The hollow of the pipe is „removed“. For full-section pipes it doesn´t get substracted (the hollow even doesn´t exist) but the rest of the equation is the same. Consequently that the moment of resistance is a bit higher.

Hollow pipes are often prefered because they need less material, they are lighter and their moment of resistance is not very much lower than the moment of resistance of full-section pipes.

You can find another hollow pipe between the bottom and the top of the platform which guarantees the stability in the middle of the platform.

 

Those are all important structures of our platform. Their interaction causes that an ordinary piece of paper can resist to up to 400g (1 pound-lb = 453,59g).