Understanding of cylinders and cones

Teaching objective: 1. Through teaching, students can comprehensively and accurately grasp the basic characteristics of cylinders and cones and the names of each part.

2, through observation, imagination, operation, discussion and other activities, cultivate students' ability of independent inquiry, a lot of practice and innovation.

3. Use the scenarios provided by CAI courseware to stimulate students' enthusiasm for active participation in learning, and initially penetrate the dialectical thought of the law of development and change of things under certain conditions.

Teaching emphasis and difficulty: master the basic characteristics of cylinders and cones and the names of each part completely and accurately. first kind

(1) review

1。 After reviewing the names and characteristics of the three-dimensional graphics (cuboid and cube) that have been learned, let the students "touch" the desktop and feel that these surfaces are "flat" again.

2。 Show objects in the shape of cylinders and cones.

Q: Can the shapes of these objects be called cuboids or cubes? (Can't) What's that called?

Writing on the blackboard: understanding of cylinders and cones

Students, today we will learn about cylinders and cones to see what their characteristics are.

Learning new knowledge

1。 Create a scene and get a chance to play.

(1) Cai offers several kinds of ice cream accompanied by light music.

These objects are divided into several types (not) according to their shapes.

What are their shapes? Let's talk about it (some students use gestures to say: they are all round and tall; Some people say they are like cylinders ...)

Teacher's Note: They are all cylinders.

Some students gesticulated: they are all sharp; ……)

Teacher's Note: These are all cones.

(2) Please close your eyes and imagine the shapes of cylinders and cones.

2。 Further explore the surface characteristics of the cylinder. Ask the students to prepare cylinders and cones.

(1) Touch: What are the characteristics of the upper and lower surfaces of a cylinder and a cone?

(2) Discussion: How do you know? What method can be used to prove it?

(Measure the diameter or compare the bottom with a circle on paper) Show CAI courseware for verification.

(3) Touch again: What else? (This is a surface)

(4) Experimental verification: Students begin to put the side of the cylinder on the desktop. Can a math book be placed on the side? Try it (the highlight is a surface).

Tell the students that this surface is called the "side" of the cylinder.

(5) Guided generalization: (CAI display)

Surface characteristics of the cone: the bottom is round.

The side is curved.

Teacher's explanation: today we are all learning three-dimensional figures like this, which are straight, as thick as the top and bottom, like cylinders. We call it a cylinder. Below is a circle with a sharp top, which is called cone.

Exercise: What other cylinders and cones have you seen in your daily life? (oral answer)

3。 The height of the cylinder.

CAI display:

(1) Question: Which is tall and which is short? What does this have to do with the cylinder?

(The conclusion is that the height of the cylinder is related to the distance between the opposite faces of the cylinder.)

(2) Question: How to measure the distance between two bottom surfaces?

(Guiding perception: the distance between the centers of two bottom surfaces should be measured) (Cai demonstrates the process of height cutting)

(3) Ask again: Is the column only this high?

(4) Cai Verification: There are countless heights.

(5) Discussion: If the height of a cylinder is to be measured, where is the most convenient place to measure it? How to measure?

The methods are as follows: (1) Measure with the right-angled edge of the triangle; (2) Measure by the side with a ruler; ③ Draw the cylinder side on the paper;

……

(6) Practice, asking students to measure the height of a cylinder by computer operation. 4, the height of the cone

How to find the height of a cone? The distance between the apex and the center of the bottom of the cone is the height of the cone.

(3) Summary

What did you learn in this class today?

class exercise

Do exercises 1 and 2 by yourself.

Second lesson

Complete independent exercises 3-6.

Question 3: It is the topic of cultivating students' imagination and establishing the concept of space. The purpose is to pave the way for students to further study the cone lateral area. When practicing, students can think first and then contact. It can also be a student's hands-on topic. I want students to find some objects shown on the way and cut them along the height to get a preliminary understanding of the sides of cylinders and cones.

Question 4: It is an operational topic. In practice, students can roll up with a rectangular paper roll first, and then exchange different rolling methods to draw different conclusions. At the same time, it also paves the way for the future study of lateral area.

Question 5: It is a topic to cultivate students' spatial imagination. Ask the students to prepare rectangles, semicircles, triangles and flags before class. When practicing, let the students rotate quickly to see which figures are formed, and cultivate students' imagination of spatial figures.

Question 6: It is a difficult choice to solve practical problems. In practice, let students know the relationship between each part of the ribbon and the original height and bottom diameter, and answer with the knowledge of cylinder.

"Extracurricular practice" is to let students find cylindrical and conical objects in their lives and measure the diameter and height of the bottom. Teachers should guide students to master the correct operation method of measuring the height of the cone: (1) First, level the bottom of the cone; (2) horizontally placing a wooden board at the top of the cone; (3) vertically measure the distance between the flat plate and the bottom surface;

Surface area of cylinder

Teaching objective: 1. Understand and master the names of cylinder parts, and establish the concept of cylinder space;

2, master the calculation method of cylinder side area, surface area, and can be applied.

Teaching emphases and difficulties: 1. Teaching emphasis: derivation of calculation method of cylindrical side area.

2. Teaching difficulty: the derivation process of lateral area formula of cylinder.

Teaching aid preparation: learning kit for teaching courseware

first kind

Review preparation

Teacher: How to find the area of a rectangle?

Health: Rectangular area = length × width. (Teacher writes on the blackboard)

The teacher took out squares and circles. Ask the same question.

Teacher: What are the formulas for the area and circumference of a circle? What conditions can be given to find the area and perimeter of a circle?

Then stick the circle on the rectangle. Then do some exercises about the area and circumference of a circle.

Is this useful? . . . Qingdao Road 105: Licun Park-Liuting Market Licun 5:30- 19:40 Liuting Market 6: 10-20:20 Departure: Licun Park-Licun Park-Hushan Road-Xiufeng Road-Dongda Village. . so this is it？