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Find the coordinate of the centroid for the shaded part of the lamina with respect to given reference axis.[Figure: origin O with x-axis to the right and y-axis upward. A semicircle of radius R = 8 cm (the digit is partly obscured in the scan; read a…

Q.2 (A) Find the coordinate of the centroid for the shaded part of the lamina with respect to given reference axis.

[Figure: origin O with x-axis to the right and y-axis upward. A semicircle of radius R = 8 cm (the digit is partly obscured in the scan; read as 8 cm, consistent with the drawing) centred at O lies below the x-axis, spanning x = −8 cm to x = 8 cm. A right-angled triangle lies above the x-axis with one vertex at O, base along the x-axis from O to x = 8 cm, vertical side at x = 8 cm, and hypotenuse from O at 60° to the x-axis. A semicircle of radius r = 3 cm, below the x-axis with its diameter on the x-axis from x = −8 cm to x = −2 cm (centre at (−5, 0)), is cut out. The remaining region (big semicircle + triangle − small semicircle) is shaded.]

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Components (cm): triangle height \(h = 8\tan60^\circ = 13.856\) cm.

PartA (cm²)x (cm)y (cm)AxAy
1 Semicircle R = 8 (below x-axis)\(\pi 8^2/2 = 100.531\)0\(-4R/3\pi = -3.395\)0−341.333
2 Triangle (base 8, height 13.856)55.426\(\tfrac23 \times 8 = 5.333\)\(13.856/3 = 4.619\)295.603256.000
3 Semicircle r = 3 (removed)−14.137−5\(-4r/3\pi = -1.273\)+70.686+18.000
Σ141.819366.289−67.333

\(\bar x = \dfrac{366.289}{141.819} = 2.583\) cm, \(\bar y = \dfrac{-67.333}{141.819} = -0.475\) cm

Answer: centroid G = (2.583 cm, −0.475 cm) w.r.t. O.

Doubtly AI · 25 Oct 2026 AI-verified · Oct 2026 Report
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