Question

which shape best describes the object generated when the half circle is rotated about the axis?
solid sphere
hollow sphere
hollow cylinder
solid cylinder

Explanation:

When a half - circle (semicircle) is rotated about its diameter (the axis in the given figure), every point on the semicircle traces out a circular path. The set of all these points forms a three - dimensional object. A solid sphere is formed because the entire area of the semicircle (including the interior) is rotated. A hollow sphere would imply that only the boundary (the arc of the semicircle) is rotated, but the problem shows a filled - in semicircle (the half - circle with an area). A cylinder (hollow or solid) is formed by rotating a rectangle or a line segment about an axis, not a semicircle.

Answer:

solid sphere