Are there any brain boxes out there who could work this out?

I'm kinda stuck on my phisics homework. I get the whole pressure thing, but when you find the area of a shape, is it the same as finding the area of a 3D shape? And could you give me advice on how to find the area of a 3D shape? Thanx so much x


Are there any brain boxes out there who could work this out?
Finding the area of a 3D shape is non-trivial. So I'll suggest 2-3 approaches.





(Approach 1) Standard geometric shapes


If the object has standard geometric form e.g., sphere, cube, cylinder etc., there are well known equations for calculating their surface area. For example, area of a closed (with 2 end caps) cylinder is sum of the 2 circular ends + the long middle part i.e., (2* Pi*r^2) + (2*Pi*r*h), where r is the radius and h is the height or length of the cylinder





***BTW, what Sham said above: cylinders = 2( r2) + (2 r) * h) is the wrong formula. It is missing the ';Pi';


Also 3-D shapes DO NOT have infinite planar area -- else if would take infinite amount of paint to paint a 3D object, LOL





(Approach 2) Mapping into linear pieces


If the object does not have a standard geometric shape, you can still map it into smaller piecewise linear approximations by breaking it down into smaller squares and triangles, whose areas you can then add up to calculate the total surface area. This is exactly what is done today in many 3D graphics and gaming engines, where the object is approximated by increasingly smaller geometric shapes (polygons)





(3) Measuring Pressure


If the object is a hollow, sealed, incompressible fluid system, any pressure applied on it will be transmitted equally in all directions and Pressure = Force/Area. So by knowing the force exerted and the pressure felt, you can calculate the area





Unfortunately #3 doesn't work with solid objects e.g., irregular rocks. So you will need to resort to method #2





If you have more specifics, I may be able to suggest a better solution. So drop me an email.





I hope this helps. Good luck!





EDIT: **@Sham ** -- How did you try to type ';Pi'; in YA? Just use the word ';Pi'; instead so YA doesn't get messed up. BTW, I'm not sure what you mean by ';Pi = R'; because you don't have any ';R'; in your answer... or some how it is not showing up at least. Please drop me an email - I'd like to understand your answer better. BTW, emails to you don't seem to be working. What happened?Are there any brain boxes out there who could work this out?
I'm not sure if you are asking about the difference between area and volume, or are just finding area of 2-D shapes and surface area of 3-D shapes.





The area of a 2-D shape is generally LxW, but this formula varies depending on the shape, and there may be no formula for an irregular shape. For a 3-D shape, the added dimension must be accounted for. This makes the interior space a volume instead of an area. Thus, volume is generally LxWxH for a regular shape.





Somewhere in one of your textbooks there should be a list of formulas for finding the areas (or volume in a 3-D shape) of various 2-D and 3-D shapes.
Try ';surface area';. If 3-D shapes had a true planar area, it would be infinite.





Each 3D Shape has its own equation to work it out such as cylinders = 2( r2) + (2 r) * h





Provide further info on what shape.. I'l see what i can do =)





EDIT: the ';pi'; = R.. YA Wont let me insert tht stpid symbol lol x