Centre of gravity of a right-angled triangle A statement claims: “The centre of gravity (centroid) of a right-angled triangle lies at its geometrical centre.” Determine whether this statement is correct or incorrect.

Difficulty: Easy

Correct Answer: Incorrect

Explanation:

Introduction / Context:In statics and engineering mechanics, the centroid (centre of gravity in a uniform field) of standard plane figures is a frequently used result. Right-angled triangles are common in structural and area-moment problems.

Given Data / Assumptions:

  • Uniform thickness and density so CG coincides with geometric centroid.
  • Right triangle with legs of lengths b and h meeting at the right angle.

Concept / Approach:The centroid of a triangle lies at the intersection of its medians. For a right-angled triangle, measured from the right-angled vertex along the legs, the centroid coordinates are x̄ = b/3 and ȳ = h/3. This is not the “geometrical centre” in the sense of the midpoint of a bounding rectangle or the triangle’s circumcenter.

Step-by-Step Solution:

Locate medians from each vertex to the midpoint of the opposite side.Their intersection point (centroid) divides each median in a 2:1 ratio from the vertex.For a right triangle with legs b and h: centroid is at (b/3, h/3) from the right-angled vertex.This is not the “centre” of the figure in a symmetric sense (triangles are not centrally symmetric), so the statement is incorrect.

Verification / Alternative check:Using area-integration: x̄ = (1/A)∫x dA over the triangular region yields x̄ = b/3 and similarly ȳ = h/3, confirming the standard centroid location.

Why Other Options Are Wrong:

  • “Correct” would imply a symmetric centre; a right triangle lacks central symmetry.

Common Pitfalls:Confusing centroid with circumcenter or incenter; these are distinct triangle centres and lie at different locations.

Final Answer:Incorrect

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