Round Bodies. Cylinder. Cone

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This lesson is suitable for students of various ages. 

Nowadays, sections of round bodies are widely used in science, technology, and daily life. Therefore, it’s important to develop knowledge in this area for further improvements in life.

Questions for students:

  • What are round bodies?
  • Where can we encounter round bodies in daily life?

A water barrel is shaped like a cylinder. Translated from Latin and Greek, “cylinder” means “papyrus.” You can take a sheet of paper and roll it into a tube; as a result, we get something similar to a cylinder. Why is a cylinder considered a round body? Look at what forms at the base? A circle. The bottom and top base of a cylinder are circles. A cylinder is also called a solid of revolution. Think about why?

A cylinder can be obtained by rotating a rectangle around one of its sides. Take a textbook and demonstrate. How can a cylinder be obtained by rotating it around one of the sides? Each child should work with rotating the textbook to understand why a cylinder is a rotation body.

One of the methods to develop spatial understanding during geometry lessons, especially in classes with visually impaired students, is modeling. A cylinder can be made out of paper or soft wire.

What happens if we cut the lateral surface of the cylinder along a generatrix? If we cut the lateral surface of the cylinder along a generatrix and unfold it, we will get a rectangle, which is called the net of the lateral surface.

The side surface of the cylinder. Cylinder Model

Visually impaired students perform all constructions after working with models, relying on the teacher’s commentary.

The next round object we’ll examine is a cone. In Greek, it means “peak.” The Sorting Hat in the Harry Potter universe was shaped like a cone. What other items in everyday life are cone-shaped? Ice cream cones, traffic cones, and kitchen utensils often take the form of a cone.

Cone model

You can make a cone by yourself. You can take a sheet of paper and roll it into a funnel. The funnel will take the shape of a cone. You can also cut out a circle from a piece of paper, cut a triangular wedge in the circle, and glue the cut sides together. Every student should have a model of a cone.

Why do we say that a cone is a round body? A cone has a rounded shape. At the base of the cone lies a circle. Why do we say that a cone is a body of rotation? As a result of rotating which figure is a cone obtained? A cone can be constructed as a result of rotating a right-angled triangle around one of its legs. This leg becomes the axis of the cone.

What happens if we cut the cone along a generatrix? We get the development of the lateral surface of the cone – a circular sector. Visually impaired students perform drawings under the teacher’s commentary. The teacher should speak clearly, distinctly, and understandably. It is best for the visually impaired student to perform drawings with a magnifying glass over the table.

I propose a game for the students. The rules of the game are as follows:

In an opaque bag are various household items that have the shape of bodies of rotation (a book, a tin can, a funnel, a roll of toilet paper, etc.). The student closes their eyes, randomly picks an item, and without opening their eyes identifies the item, tells us the name of the item, and its shape.