A little knowledge of grams and kilograms 1. How do pupils explain the relationship between grams and kilograms?
Fully provide students with the opportunity to "do mathematics" and let students actively construct knowledge.
Students form the representation of grams and kilograms through the activities of weighing, guessing and weighing, and then fully weigh, feel and list many items weighing about 1 gram in life. Through a lot of calculations, such as weighing 2 cents, math books, 1 kg salt, schoolbags, etc. Students are becoming more and more clear and profound about the quality concept of grams and kilograms.
Students gradually developed from "gram is light" and "1kg is a little heavy" to weighing, estimating and knowing the mass of objects with springs. Mathematics in these lives is not taught by teachers, but experienced by children themselves, forming certain skills and gaining positive emotional experience.
2. The application problems of grams and grams and kilograms in the third grade.
1. A piece of rubber weighs 5 grams. How much do six such erasers weigh?
2. Xiaohua weighs 26 Jin, and Xiao Fang weighs 23 Jin. How many kilograms is Xiaohua heavier than Xiao Fang?
3. Xiao Fang holds two toys and weighs them together. * * * weighs 30 kilograms and each toy weighs 2 kilograms. How many kilograms does Xiao Fang weigh?
The canteen delivered 60 kilograms of rice on the first day and 40 kilograms of rice on the second day. These rice are planned to be eaten for 5 days. How many kilograms do you eat on average every day?
The oil press squeezes out 8 kilograms of oil every hour. This oil press has been working for 7 hours. How many kilograms do we have to squeeze to complete the task of 100 kilograms?
1, Xiaodong bought 8 Jin of watermelon with 20 yuan money and picked it up in 4 yuan. How much is a kilo of watermelon?
2. Dad bought 3000 grams of soybean oil, ate 1000 grams, and bought 2000 grams of vegetable oil. How many kilograms of oil are there?
3. The original rice in the canteen was 1300 kg. After eating 300 kg, how many kg is left? Later, I bought 1000 Jin, and now there are Jin of rice in the canteen?
There are two glasses of water. The first glass weighs 240 grams, the second glass weighs 200 grams, and how many grams does the second glass weigh? How many grams are there in two glasses of water?
A basket of pears weighs 48kg. Four people buy a basket, 2 Jin of pears per Jin. How much should everyone pay?
6. Mom bought a big loaf of bread, weighing190g, and four small steamed buns, each weighing 50g. How much do these breads weigh?
3. Second-grade math application problems, volume II, grams and kilograms, three books a day.
This is the topic.
1, Xiaodong bought 8 Jin of watermelon with 20 yuan money and picked it up in 4 yuan. How much is a kilo of watermelon?
2. Dad bought 3000 grams of soybean oil, ate 1000 grams, and bought 2000 grams of vegetable oil. How many kilograms of oil are there?
3. The original rice in the canteen was 1300 kg. After eating 300 kg, how many kg is left? Later, I bought 1000 Jin, and now there are Jin of rice in the canteen? There are two glasses of water. The first glass weighs 240 grams, the second glass weighs 200 grams, and how many grams does the second glass weigh? How many grams are there in two glasses of water? A basket of pears weighs 48kg. Four people buy a basket, 2 Jin of pears per Jin. How much should everyone pay?
6. Mom bought a big loaf of bread, weighing190g, and four small steamed buns, each weighing 50g. How much do these breads weigh?
I wish you progress in your study!
4. The story of grams and kilograms.
Kg and Dick are brothers. Both of them think they are very capable and often blush.
One day, Miss Pigeon invited Kg and Dick to her home. Miss Pigeon wants to weigh a pair of gold earrings she just bought from a gold shop, so she asks Kg and Dick for help. Kg said eagerly, "I'll weigh it." They seem to have no weight.
How can there be no weight? Dick said, "I weighed it, 5.8 grams." Miss Pigeon smiled and said, "Yes, yes. "
Seeing Kg dejected and despondent, Dick said happily, "I'm good at it anyway."
Kg blushed and left without saying a word.
A few days later, the Monkey King held a birthday party and invited Kg and Dick to the party. "Thank you for coming. I bought a lot of fruit today. Please enjoy it. "
Dick saw the opportunity to show himself again and said proudly, "Monkey, I'll weigh it for you again."
As soon as Tang Ke weighed it, he cried. The Monkey King ran over and saw that Keke was overwhelmed.
Kg smiled and said, "I'll do it." As a result, 7.5 kilograms of watermelon, 8 kilograms of apples, 5 kilograms of peaches and 6 kilograms of Sydney were easily weighed.
Seeing Dick unhappy, the Monkey King said, "You and the kilogram are both weight units, and each has its own advantages and disadvantages. If we can help each other, all problems can be solved well. "
After listening to the Monkey King's words, both Kg and Dick extended a friendly hand and gave in to each other from now on!
The real background of the story:
In the international system of units, grams and kilograms are units of mass and one of the seven basic units of the international system of units. After the French Revolution, it was formulated by the French Academy of Sciences. Originally intended to be a newly issued standard device gram, the main unit of quality. However, due to the limitation of technology and measurement technology at that time, a standard device with the mass of 1000 times of gram was made, that is, the kilogram standard original device, which is also the reason why the mass unit in the international system of units is kilogram instead of gram. The original definition is related to the unit of length; 179 1 year: 4℃ 1 cubic decimeter of pure water. The original device was platinum-iridium alloy, which was preserved in Paris and later called the international kilogram original device. 190 1 the third international metrology conference stipulated that the kilogram is the unit of mass (not weight), which is equal to the original international kilogram. The kilogram is represented by the symbol kg. The kilogram force is a commonly used unit of measurement in engineering technology, which is defined as the gravity of the international kilogram original device at the sea level of latitude 45. The symbol is kgf. The word "force" is often omitted in engineering books, which is easily confused with the unit of quality. So in the last century, China stipulated that the use of gravity is also called weight, and the unit is kilogram force. In April 2008, researchers from the National Institute of Metrology in Brunswick, Germany, said that they would use pure silicon with a diameter of 10 cm (4 inches) to define a more standard measurement method than the current definition of kilogram mass. At present, a platinum-iridium cylinder with the closest mass to kilograms, as an internationally unified unit of weight, has been kept in a heavily guarded vault outside Paris, France. However, due to consumption and wear, its mass is slowly decreasing, the accuracy of basic units is affected, and the error is getting bigger and bigger. The new pure silicon fuselage is really special, and the construction cost is 2 million euros (about 3.2 million US dollars). Pure silicon combines the strength of Russian, Australian and German scientific elites. It takes five years to manufacture, and the weight is infinitely close to one kilogram. This is a perfect sphere with high purity. 99.99% of the substance is a silicon isotope called silicon 28. Scientists in Brunswick, Germany will conduct thousands of experiments on pure silicon from now on to calculate the number of silicon atoms that make up pure silicon.
5. Knowledge of kilograms, grams and tons
1. kg: kg is the basic unit for measuring quality in the international system of units, and it is also one of the most commonly used basic units in daily life.
One kilogram is defined as the mass of the international kilogram original device, which is almost as heavy as one liter of water. One kilogram equals one kilogram, which is equivalent to two kilograms in China.
For example, 1, a liter of water is 1km2, a fish is 2.5kg 3, and a bag of rice is 5kg 2. Gram is the unit of mass, and one thousandth of a kilogram is18 *14074481c-648. Dq is usually used to measure smaller things.
For example: 1, a bag of salt is 500g 2, a book is 300g 3, an eraser is 5g 3, and a ton: 1 ton is 1000kg, which is often used to measure the weight of larger items in life. For example: 1, a rhinoceros weighs about 1 ton.
2. The weight of whales can exceed100t. The maximum bearing capacity of a bridge is 20 tons.