Question

A centroid is an object's geometric center. For an object of uniform composition, its centroid is also its center of mass. Often the centroid of a complex composite body is found by, first, cutting the body into regular shaped segments, and then by calculating the weighted average of the segments' centroids.An object is made from a uniform piece of sheet metal. The object has dimensions of a

Answer 1

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A centroid is an object's geometric center. For an object of uniform composition, its centroid is also its center of mass. Often the centroid of a complex composite body is found by, first, cutting the body into regular shaped segments, and then by calculating the weighted average of the segments' centroids.

An object is made from a uniform piece of sheet metal. The object has dimensions of α = 1.50 ft, where α is the diameter the semi-circle, b= 3.51 ft, and c = 2.20 ft. A hole with diameter d = 0.500 ft is centered at ( 1.21, 0.750 ).

Find x", y", the coordinates of the body's centroid.

Answer:

x" = 1.4857 ft

y" = 0.668 ft

Explanation:

Given the data in the question and as illustrated in the second image below;

from the image;

BC² = DC² - BD²

BC² = 2.2² - 1.5² = 4.84 - 2.25 = 2.59

BC = √2.59 = 1.61 ft

AB = 3.51 ft - 0.75 ft - 1.61 ft = 1.15 ft

so;

A₁ = $\frac{1}{2}$ × 1.51 ft × 1.61 ft  = 1.2075 ft²

x₁ = 0.75 + 1.15 + $\frac{1}{3}$(1.61 ft) = 2.44 ft

y₁ = $\frac{1}{3}$(1.5 ft) = 0.5 ft

A₂ = 1.15 ft × 1.5 ft = 1.725 ft²

x₂ = 0.75 ft + ( 1.15/2 )ft = 1.325 ft

y₂ = ( 1.5/2 ) ft = 0.75 ft

A₃ = $\frac{\pi }{2}$(0.75 ft)² = 0.88 ft²

x₃ = 0.75 - ($\frac{4 }{3\pi }$(0.75 ft)) = 0.43 ft

y₃ = 0.75 ft

diameter d = 0.5 ft and centered at ( 1.21, 0.750 )

A₄ = $\frac{\pi }{4}$( d )² =  

x₄ = 1.21 ft

y₄ = 0.75 ft

Thus;

x" = $\frac{A_1 x_1 + A_2 x_2 + A_3 x_3 - A_4x_4 }{A_1+A_2+A_3-A_4}$

so we substitute

x" = $\frac{(1.2075X2.44) + (1.725 X 1.325) + (0.88X0.43) - (0.196 X 1.21 )}{ ( 1.2075 + 1.725 + 0.88 - 0.196 )}$

x" = $\frac{ (2.9463 + 2.285625 + 0.3784 - 0.23716)}{ 3.6165 }$

x" = 5.373165 / 3.6165

x" = 1.4857 ft

y" = $\frac{A_1 y_1 + A_2 y_2 + A_3 y_3 - A_4y_4 }{A_1+A_2+A_3-A_4}$

so we substitute

y" = $\frac{(1.2075X0.5) + (1.725 X 0.75) + (0.88X0.75) - (0.196 X 0.75 )}{ ( 1.2075 + 1.725 + 0.88 - 0.196 )}$

y" = $\frac{ (0.60375 + 1.29375 + 0.66 - 0.14112)}{ 3.6165 }$

y" = 2.41638 / 3.6165

y" = 0.668 ft

Therefore,

x" = 1.4857 ft

y" = 0.668 ft