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What is the effective stress principle in soil mechanics?
As early as 1923, K. Terzaghi put forward the basic concept of effective stress principle, which clarified the significant difference between granular materials and continuous solid materials in stress-strain relationship, thus making soil mechanics an important sign of an independent discipline
Additional stress of soil mechanics
2. It is known that the length of rectangular foundation is l, the width is B, and l > 5B,
The additional stress at the bottom of the foundation is σ 0 = 100KPA
The additional stresses in the foundation at depths of 0, 0.25b, 0.50b, 1.0b, 2.0B and 3.0b are calculated
Because of the complexity of soil mechanics research object, many soil mechanics theories are derived under ideal conditions, and are generally modified in application
The concept of linear equation of one variable is as follows______ ．
The concept of one variable linear equation: the equation with an unknown number and the highest degree of the unknown number is one variable linear equation. So the answer is: the equation with an unknown number and the highest degree of the unknown number is one variable linear equation
What is the definition of linear equation of one variable
If there is only one unknowns, and the formulas containing unknowns are all integers, and the degree of unknowns is 1, such an equation is called linear equation with one variable, and the usual form is ax + B = 0 (a, B are constants, and a ≠ 0)
The concept of linear equation of one variable is as follows______ ．
The concept of one variable linear equation: the equation with an unknown number and the highest degree of the unknown number is one variable linear equation. So the answer is: the equation with an unknown number and the highest degree of the unknown number is one variable linear equation
The definition of solving linear equation with one variable
An equation with only one unknown number and the degree of the unknown number is 1 is called one variable linear equation
From a Class A to B, which is 20 kilometers away, half of them take the car first, the other half walk first, and they start at the same time. The first person who takes the car gets off at B on the way to walk instead, and the car immediately drives back to pick up the other half of the walkers, so that they can get to B by car. As a result, the two teams arrive at the same time. It is known that the walking speed is 8 kilometers per hour, and the car speed is 40 kilometers per hour, How many hours does it take from place a to place B?
Suppose that the time for transporting the first batch of people is x and the time for transporting the second batch of people is y
8x + （40x-8x）*8/(40 + 8）+ 40y = 20
40x + （40x-8x）*8/(40 + 8）+ 8y = 20
The solution is x = 3 / 8; y = 3 / 8
The total time is: x + (40x-8x) / (40 + 8) + y = 1 (hour)
A plane with a speed of 1200 km / h in the absence of wind takes 3 hours to fly an X km route against the wind, and 2 hours to fly this route along the wind, so the length of this route can be calculated
Let the wind speed be y km / h
1200-y=x/3
1200+y=x/2
x=2880
Y = 240, so the route is 2880 km long
Who has an example of one variable linear equation in seventh grade mathematics
There is an analytical settlement
1、 Fill in the blanks (5 points for each blank, 40 points in total)
1. If x = 2 is the solution of equation 2x-a = 7, then a =_______
5. The equation 2X-4 = 3M and X + 2 = m have the same root, then M = M_________
7. If M-N = 1, then the value of 4-2m + 2n is___________
8. The teachers of a certain school go out for four days on holiday. The sum of the four days is 42, so what are the dates of the four days______________
2、 Multiple choice questions (5 points for each question, 30 points in total)
2. If x = 2 is the solution of the equation K (2x-1) = KX + 7, then the value of K is ()
A.1 B.－1 C.7 D.－7
3. There are five lights in a classroom, including two kinds of 40 Watt and 60 watt. The total wattage is 260 watt. Then the number of 40 Watt and 60 watt bulbs is ()
A.1,4 B.2,3 C.3,2 D.4,1
4. The turnover of a store last month is million yuan, which is 15% higher than that of last month, so the turnover of this month is ()
A. (M + 1) · 15% ten thousand yuan b.15% ten thousand yuan
C. (1 + 15%) m ten thousand yuan D. (1 + 15%) 2m ten thousand yuan
5. Aunt Li deposits 2000 yuan into the bank for a fixed period of one year. After deducting 20% of the interest, she gets the sum of principal and interest of 2120 yuan. If the annual interest rate of this kind of deposit is x, then the equation ()
A.2000（1＋x）＝2120 B.2000（1＋x％）＝2120
C.2000（1＋x·80％）＝2120 D.2000（1＋x·20％）＝2120
6. Xiaoming's father bought back two carpets. He told Xiaoming that the area of the small carpet was exactly 1 / 3 of the area of the large carpet, and the sum of the two carpets was 20 square meters. Xiaoming soon came to the conclusion that the areas of the two carpets were (unit: square meters) ()
3、 Answer questions (10 points for each question, 30 points in total)
1
The value of X of
3. Xiaoming found that the unit price of Walkman and schoolbag is the same in a and B supermarkets. The sum of the unit price of Walkman and schoolbag is 452 yuan, and the unit price of Walkman is 4 times that of schoolbag, less than 8 yuan
(1) How much is the unit price of the Walkman and schoolbag that Xiaoming wants?
(2) If all the goods in supermarket a are sold at 20% discount, and if supermarket B is full of 100 yuan, 30 yuan will be returned to the coupon (if less than 100 yuan is not returned, the coupon is universal). Xiaoming only brings 400 yuan. If he only buys these two items in one supermarket, can you explain which supermarket he can buy them in? If both can choose, which supermarket will save more money?
[answer]
1、 Fill in the blanks
1. - 3 2.9 3. X = 0 4.2x - 1 = 0, etc
5.－8
It is suggested that from the equation 2X-4 = 3M
From the equation x + 2 = m, we get x = m-2
The solution is m = - 8
6.－3
So m = - 3
seven point two
It is suggested that 4-2m + 2n = 4-2 (m-n) = 4-2 × 1 = 2
9, 10, 11, 12
2、 Multiple choice questions
1.D 2.C 3.B 4.C 5.C 6.C
Three
1. Remove the brackets
The results are as follows
If the item is transferred, the following results can be obtained:
The results are as follows
3. (1) if the unit price of schoolbag is x yuan, the unit price of Walkman is (4x-8) yuan
According to the meaning of the title:
Answer: the unit price of Walkman is 360 yuan, and that of schoolbag is 92 yuan
(2) If you buy in supermarket a: 452 × 80% = 361.6 yuan
At this time, Xiaoming still has: 400-361.6 = 38.4 yuan
If you buy it in supermarket B, he will first spend 360 yuan to buy a Walkman and return the shopping Voucher:
At this time, you can buy a schoolbag with the rest: (90 + 40) - 92 = 38 yuan
Because 38.4 > 38
So Xiaoming two supermarkets can choose, but he in a supermarket to buy more money
In a workshop, each worker can process 15 screws or 10 nuts per day. There are 60 workers in the workshop. How to arrange workers so that one screw can be matched with two nuts?
Solving the X-man problem of screw production
15x=10（60-x）÷2
15x=300-5x
20x=300
x=15
Production of nuts: 60-15 = 45 people
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