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Lo.Lee.Ta.
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Homework Statement
An appliance box has a square base with sides of length L, and has rectangular sides with a height of 3L. The top of the box is missing. The box is made from cardboard of uniform thickness and density. What is the height of the center of mass of this open box, with respect to the bottom of the box?
Homework Equations
Equation for the center of mass is: C.M.(x) = [(m1)(x1) + (m2)(x2) +...]/[m1 + m2 +..]
C.M.(y) = [(m1)(y1) + (m2)(y2) +...]/[m1 + m2 +..]
The Attempt at a Solution
This fellow on Yahoo Answers responded to this same question with the right answer. I am just confused about his solution... This is what he/she had written:
4 x 3L^2 x 3L/2 = 18L^3
total mass of box = 4 x 3L^2 + L^2 = 13L^2
18L^3/13L^2 = 18/13L
That is the right answer: 18/13L. But I just don't see how this method worked...
So the person squared the height of the box, and then multiplied that by 4. Why did he/she do that? That does not seem to be apart of the above formula... And then he multiplied that answer by L squared... Why are things even squared in order to solve the problem?
...As you can see, I don't get it at all... :/ Please explain this to me! Please help me to understand what each thing means in the solving of this problem!
Thank you so much for helping me! You are awesome! :)
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