ANSWERS: 5

Do you know the dimensions of the circle? if you know the radius of the circle it doesn't matter where the circle is..just pi r squared to get the area of the circle and subtract from the total area of the rectangle

Heres a picture of the real thing. I get stuck when i have subtracted the area of the hole. What to do next?

Please use the indications on this page: "This method is useful when you wish to find the center of gravity of an object that is easily divided into elementary shapes, whose centers of mass are easy to find (see List of centroids). We will only be finding the center of mass in the x direction here. The same procedure may be followed to locate the center of mass in the y direction. The shape. It is easily divided into a square, triangle, and circle. Note that the circle will have negative area. From the List of centroids, we note the coordinates of the individual centroids." http://en.wikipedia.org/wiki/Center_of_mass#Locating_the_center_of_mass_of_a_composite_shape

Thanks for your answers really good! =)

I'll choose a coordinate system based in the lower left corner. Before we cut the hole, the rectangular solid has a center of mass at coordinates (27.5, 12.5) Let's make the thickness of this piece T, and the density p. The total mass, before cutting the holes is 50*25*T*p Now calculate the mass and center of mass of the material removed from each of the holes. The volume of the left hole is pi*4^2*25. Its mass is pi*4^2*25*p Its center of mass is (15,12.5) The volume of the right hole is pi*5^2*T Its mass is pi*5^2*T*p Its center of mass is (40,15) Center of mass is the sum of (coordinates of something * mass_of_each_thing) divided by the sum of the masses. Here the holes are acting as subtracted masses. So compute (25.5, 12.5)*50*25*T*p  (15,12.5)*pi*4^2*25*p  (40,15)*pi*5^2*T*p and divide it by (50*25*T*p  pi*4^2*25*p  pi*5^2*T*p)
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