Question

Use strip and fasteners to make a triangle and a quadrilateral.

Try to push inward at any one vertex of the triangle.

Do the same to the quadrilateral.

$\mathrm{Q}1$ Which one of them will get distorted ?

$Q2$ Why is it that structures like electric towers make use of triangular shapes and not quadrilateral ?

Answer 1

According to Basic property of Triangle:

The triangle is a polygon that does not change its shape without changing the length of its sides.

For all other polygons like Quadrilaterals, the shape can be changed by changing four or more angles.

Solution 1 : On moving the vertex of triangle, whole triangle moves, but the shape remains same.

So triangle is rigid.

But on moving the vertices of quadrilateral the shape of quadrilateral become distorted.

Solution 2: Electric towers make use of triangular shapes because they are more rigid then other polygons like Quadrilaterals.

Hence, triangles are more rigid then quadrilaterals.