Help with a few junior high school questions, and help with a few junior high school questions

1.When the gas pressure in the pressure cooker exceeds the safe value, the gas in the pot will rush out of the pressure limiting valve, and the gas will run out of a part, so that the gas pressure in the pot will be reduced. There is a pressure cooker with a diameter of 24 cm, a hollow column with a small hole cross-section of 10 square millimeters, and a pressure limiting valve of 100 grams

1) What is the maximum pressure that can be reached by the gas in the pressure cooker?

2) Tested by the commodity quality inspection department, the maximum pressure of the gas in the pressure cooker cannot exceed 18,000 Pa, to make the pressure cooker continue to be used safely, can the original pressure limiting valve still be used? If not, what is the mass of a pressure limiting valve? (g = 10 N kg).

2.There is water in an upside-down flask, the water in the flask has just stopped boiling, pour the flask with cold water, you can see the water boiling again, why?

3.The problem of atmospheric pressure in the second year of junior high school.

When using a syringe to absorb the liquid, push the piston of the syringe to the lower end in order to ( ) and then insert the needle into the liquid medicine and slowly pull the piston apart, so that the gas in the syringe ( ) is greater than the atmospheric pressure above the liquid medicine ( ).

4.Two objects A and B with the same initial temperature, put A into a cup of hot water, the water temperature decreases T after thermal equilibrium, take out A, put in B, the water temperature decreases T after thermal equilibrium, and the quality of water remains unchanged if there is no heat loss in the whole process, then there may be several situations in the mass and specific heat capacity of the two objects A and B?

5.If you pour a spoonful of hot water into a container with water, the temperature of the water in the container rises by 5 degrees Celsius, and if you add another spoonful of the same hot water, the temperature will rise by another 3 degrees Celsius

You go to the junior high school classification by yourself, find patience and solve the problem or, in order to solve the problem, see if there is any.

Question 1 Choose A because the more you go to the center and the king of Wu and Goujian, they are all far from the center of the border between China and foreign countries, but Zhejiang is in the center of the heart, and there can be no king of Wu and the king of Yue.

2. Question 2 chooses D, the view of the legalists is to advocate ** centralization.

Question 3 Select the Yue ethnic group.

4. Kick option B because the nationalities, people, soldiers, county orders, and so on during the Yao Shun Yu period were all very good, people didn't have to close their doors at night, and it was impossible for the army to cause chaos.

How can a hungry child be classified in physics if he is wrongly classified?

1. D (See this for details.)

2. D (Qin Shi Huang adopted the ideas of Legalism).

3. A (Qin Shi Huang conquered the southern Yue people during his reign).

4. D (Confucius opposed all wars in the Spring and Autumn Period and the Warring States Period, reflecting his negative and conservative thinking) 5. (Look at this and choose it yourself.)

I don't know if I should choose B or D).

This problem is a total of two formulas, there are two unknowns are x and y, multiplying the left and right sides of the first equation by 2 becomes 2x minus 2y equals 8. After that, the first formula is added and merged with the second formula to form a single formula. The combined formula is 6x equals 8-1.

Explain that 6x = substituting x equals 7 6 into the first equation gives y=-17 6

Since it is a junior high school math problem, one of the methods of solving a system of binary equations in junior high school is substituted for the elimination method.

Solution: Shift the term x y=4 to get x=4+y substitution solution: 4(4+y)+2y= 1

Solution: y= 3 8 is substituted into x=4+y

The solution is x=29 8

x 7/6.

y minus seventeen out of six.

1 The discriminant formula of the equation is (a+b) 2-c 2 , because a+b is greater than c, then a+b) 2 is greater than c 2, so the discriminant is greater than zero, so there are two unequal roots.

Wait, the rest will give you the process, and now there's something urgent.

1) Two different roots.

deta=(a+b)*(a+b)-c*c>0a, 1 b is the two roots of the equation 5x2+2003x+9=0, using Vedder's theorem.

It's a bit of a hassle......

It seems that it is not generally necessary to have a positive integer root, but it should probably be an integer.

Solution: 1+ 9=90°, Early 4+ 8=90°, 6= 9 2= 4 3= 5= 7=45°

Angle 1 + Angle Mu Brother Destroy 9 = 90 Angle 4 + Angle 8 = 90 Angle 6 = Angle 9 Angle 2 = Angle 4 Angle 5 = Angle 7 = Angle 3 = 45 Zai Xun Angle 2 + Angle 6 Xiaochen shouted 405 degrees.