How long is this table?
Teaching topic: How long is the desk?
Teaching content: pages 5 1 and 52 of the first volume of the second grade mathematics textbook published by Beijing Normal University.
Teaching type: new teaching
Teaching preparation: ruler, courseware
Teaching objectives:
1. Experience the process of measuring the length of the same object with different tools, and realize the necessity of unifying the length unit.
2. Know the centimeter and realize its practical significance.
3. Initially learn to measure the length of objects and lines with a scale (limited to whole centimeters), estimate the length of smaller objects, and measure the length of objects with a scale.
Teaching emphasis: let students initially establish the impression of 1 cm.
Teaching difficulty: you can measure the length of smaller objects with a scale.
Teaching process:
First, the problem situation, introduce the topic
Teacher: Look! How neatly the tables in our classroom are arranged. Do you want to know the length of these tables? (think! )。 Teacher: OK, in this class, let's learn "How long is the desk".
(Demonstration courseware II, blackboard writing topic-how long is the desk)
Second, explore independently and impart new knowledge.
1. How long is this table?
Teacher: (Stick the cardboard instead of the desk on the blackboard, and the teacher will draw the length on the cardboard while talking) The length of our desks is the same! What tool can you think of to measure its length? Who wants to talk? Students use pencils, books, hands and other tools to answer, and the teacher writes the methods on the blackboard in turn.
Teacher: OK! Who wants to measure with the tools above? (Call the students to take tools to the blackboard to measure) Writing on the blackboard:
Pencils: 3
Hand: 4 feet
Books: 2 books
Teacher: The same desk, why do you get different results? Who can tell me why? Health: Because of the different tools used, the measurement results are different.
The teacher concluded: Do you agree with her statement? (agree! ) that's right! Using different tools to measure the same object will result in different results. Only when the tools are the same, the results will be the same, so it is necessary to find a unified measure.
Measuring tools. Then what tools should we use to measure it? rule
(Demonstration Courseware 3, Revealing the Secret of Measuring Objects with a Ruler)
Activity (1) Take a look!
Teacher: Please take out the prepared ruler and observe it carefully. What did you find on the ruler?
(Demonstration Courseware 4) Student: There are numbers 0, 1, 2, 3, 4 ... There are many lines, some are long and some are short, and some are letters cm. (The teacher flashed the ruler with the students' answers)
The teacher added: the numbers are arranged in order from small to large; Three vertical lines of different lengths are called tick marks; The scale of 0 is at the far left of the ruler, indicating the starting point; The "cm" on the ruler is a commonly used unit of length and can also be expressed in centimeters. {blackboard writing: length unit-cm)}.
Teacher: How long is 1 cm?
Teacher: Please look at the big screen! The length from 0 scale to 1 is 1 cm, that is, 1cm, that is, 1 cm = 1cm. (blackboard writing: 1cm = 1cm)
Activity (2) points!
Teacher: The length from scale 0 to 1 is 1 cm, so which section on the ruler is also 1 cm? Please point it out. (Demonstration Courseware 5)
Health 1: the number 2-3 is long 1 cm.
Health 2: The numbers 4-5 are 1 cm long.
、、、、、、、、
Teacher: In a word, the length between two adjacent numbers on the ruler is 1 cm. Teacher: How long is 1 cm? Please take out the sticks prepared before class. Its length is about 1 cm. (Teacher's action demonstration) Hold the stick with your forefinger and thumb, and then slowly pull it out. At this time, the length between our forefinger and thumb is about 1 cm. All right! Shake our little hands and relax. Let's do it again. (Repeat the action just now and let the students skillfully draw the length of 1 cm by hand) Teacher: Please put the stick aside and let's play a little game, OK? (good! ) listen to the password! (Teachers and students play "take" and "put" 1 cm strokes together)
Activity (3) Find it!
1, Teacher: The students did a great job! Besides finding the length of 1 cm on the ruler, think about what objects around us are about 1 cm in length. Who wants to talk?
Teacher: The teacher will give you some hints, such as finding some parts of our bodies or our school supplies. (Demonstration Courseware 6) According to the students' answers, the teacher demonstrates courseware while speaking: the width of index finger, the width of nails, nostrils, etc. Thickness of rubber, length of staples, thickness of books, width of transparent adhesive, etc.
Teacher: In our life, there are actually many such examples. The length of an object is about 1 cm. This is for everyone to find after class.
2. Teacher: (Demonstration Courseware 7) Just now we learned how long 1 cm is, and how long is that 2 cm? Please look at the ruler. What do you mean by 2 cm long?
Health 1: 0-2 is 2 cm long.
Born 2: 2-4, 2 cm long.
Teacher: How do you know it is 2 cm long?
At this time, the teacher can guide the students to tell how many centimeters there are between them, or how many centimeters are different from each other (that is, the scale with large scale decreases)
Then ask the students to say that 2-4, 7-9 and 5-7 are all 2 cm long.
Teacher: So from where to where does it mean 5 cm long?
Health 1: 0-5 is 5cm.
Health 2: 5- 10 is 5cm.
Teacher's summary: In order to find out the length of a few centimeters on the ruler quickly and accurately, we will see whether to start from the scale of 0. If you start from the 0 scale, then the 0 scale is a few centimeters; If you don't start from the zero scale, you can see how much the difference between the two whole scales is, that is, the big scale MINUS the small scale, and the number is several centimeters.
Teacher: (Demonstration Courseware 8) Now the teacher wants to test everyone, dare to accept the challenge? (Dare! ) ok! Look at the big screen (Ask students to say how many centimeters 5-6, 0-4, 0-6, 1-5, 6-8 are in the form of quick answers) Activity (4) Measurement! (Demonstration Courseware 9)
Teacher: Knowing the measuring tool-ruler, we must learn to use it to measure the object we want to measure. The teacher has a pencil here and wants to measure its length with you.
1. Demo courseware: How long is the pencil?
Teacher: Before measuring, please estimate how long this pencil is. Who wants to talk? Teacher: Do you want to know its real length? (think! ) ok! Let's measure it and see how long it is. Look at the big screen
Teacher: Measure the length of an object with a ruler (the teacher said while demonstrating the courseware 10). We should pay attention to:
(1), put the object and the ruler flat.
(2) One end of the object is aligned with the 0 scale of the ruler.
(3) Look at the other end of the object facing the scale on the ruler. The length of the object is several centimeters.
Teacher: (demo courseware11) The scale of 0 indicates the starting point, so when measuring the length of an object, it usually starts with the scale of 0.
Yes, but how to measure it if it doesn't have a scale of 0? Who wants to talk?
Health: It can be measured by a certain number in the back.
The teacher concluded: Do you agree with her statement? (agree! ) that's right! If there is no scale of 0, you can start with a number at the back, and then subtract the small scale from the large scale when reading. The number is several centimeters.
2. Teacher: (demo courseware 12) Now, four little bears also know the ruler and want to use it to measure the length of the pencil. The bears want to invite you to act as judges to evaluate whose measurement method is right. Please follow the third question on page 5 1 of the textbook!
Teacher: Who wants to be a referee? (Answer by name)
The measurement method of 1: 1 bear is wrong, and the object is not aligned with the 0 scale.
Health 2: The measurement method of Erxiong is correct.
Health 3: The measurement method of the third bear is correct, but its result is wrong.
Health 4: The measurement method of the fourth bear is correct. 1-6 differs by 5 cm, so it is 5 cm. The students answer and the teacher demonstrates the courseware.
3. Teacher: Do you want to test yourself after you become a referee? (think! It seems that everyone can't wait, ok! Please read item (1) of question 4 on page 5 1 of the textbook, measure the length (demo courseware 13), and finish it quickly. After the students reveal the answers, the teacher demonstrates the measurement process of courseware.
Teacher: While learning to measure the length of an object with a ruler, you should also learn to draw line segments with a ruler. Then how do you draw a line segment with a ruler? Look at the big screen Draw a line 4 cm long with a ruler.
(Demonstration Courseware 14) Draw an endpoint first, align it with the 0 scale of the ruler, count the specified length, then draw another endpoint, and connect the two endpoints to get a graph that is a line segment with the specified length. Finally, in order to know the length of this line clearly, we mark it.
Teacher: The whole painting process has been demonstrated to everyone. Please finish it by yourselves in the textbook. (division patrol, individual guidance)
Third, classroom exercises-consolidation and application
In order to consolidate the new knowledge we have learned today, let's play a practice game, shall we? (good! Look at the big screen! (demo courseware 15)
1, (demo courseware 16) Level 1: I would say, how many centimeters are they?
2. (demo courseware 17) Level 2: I will test it.
Teacher: How many centimeters are our pencils, math books and exercise books? Let the students fill in the estimated data in the textbook first, and then give them time to measure. How many centimeters is it? )
3. (demo courseware 18) Level 3: I can draw a picture and draw a line 8 cm long.
(Students are named to draw on the blackboard, and the teacher will check individual instructions, and finally comment and demonstrate the courseware.)
Teacher: (demo courseware 19) Congratulations on your successful customs clearance!
Fourth, the class summary (demonstration courseware 20)
Teacher: Let's sum up what we have learned in this class.
Teacher: We know the unit of length is centimeter, and we know that centimeter can be expressed by (cm). We also know that 1 cm is about as wide as a finger, and we have learned to measure the length of an object with a ruler. I hope the students will do more related exercises after class to consolidate it!
Five: Homework (demo courseware 2 1)
After class, use what you learned today to measure the length of your desk with a ruler.
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