Question

If the shape in the [diagram] rotates about the dashed line, which solid of revolution will be formed?

A: shape 1

B: shape 2

C: shape 3

D: shape 4

Answer 1

I think it is shape 3

Answer 2

Shape 3 will be formed

Explanation:

Shape I is obviously the one obtained by rotating a single straight line around axis of symmetry. In this case a cone or frustrum of cone is obtained. But we have a funnel hence option I is incorrect

Shape II is got by rotating a trapezoid along with a line on top which gives the desired figure hence not right.

Shape 4 is got by roating a quadrant circle with another small quadrant circle on top hence incorrect.

Shape 3 is right because when we rotate the picture in the diagram around a vertical line we can get a funnel only.

THis is because straight line on top will give the cylinder part of funnel and down cone type will be given by the slant line.

Shape 3 is right