It took 50 seconds for the train to cross a 1140 meter long bridge and 80 seconds for the train to cross a 1980 meter long tunnel

It took 50 seconds for the train to cross a 1140 meter long bridge and 80 seconds for the train to cross a 1980 meter long tunnel

Set: conductor L, speed v
50*V = 1140+L
80*V = 1980+L
The solution is L = 260 m, v = 28 m / s

It takes 50 seconds for a train to pass a 1140 meter long bridge and 80 seconds for a train to pass a 1980 meter long tunnel. What is the speed of the train and its body?
Don't make equations!

Train speed = (1980-1140) / (80-50) = 28 m / S
Vehicle length = 28 × 50-1140 = 260m

It took 60 seconds for a train to cross a 1260 kilometer long bridge. It took 90 seconds for a train to cross a 2010 meter tunnel at the same speed
It took 60 seconds for a train to cross a 1260 kilometer long bridge, and 90 seconds for it to cross a 2010 meter tunnel at the same speed

Speed (2010-1260) △ 90-60) = 750 △ 30 = 25m / S
Vehicle length 60x25-1260 = 1500-1260 = 240m

What is the gradient of 4% of the road cross section
Such as the title

4% is to increase or decrease the height by 4 meters when the level is 100 meters, and the corresponding angle is 2.2906 degrees

How many mols of chlorine is needed to make 1mol ethylene react with chlorine?

If it's an addition of 1 mol of water~
If it is a substitution reaction, it needs 4mol to replace all the four h. The reaction condition is light~
According to you, it's chlorine. That's a substitution reaction~

In the drawing, aw at represents the excavation area and fill area respectively, so what does AB represent?

AB is the surface clearing, HS is the design elevation, HD is the vertical distance, DH is the height difference

1 mol ethylene is completely added with chlorine and then replaced with chlorine. Chlorine ()
A. 1molB. 4molC. 5molD. 6mol

C2H4 + Cl2 → ch2clch2cl, so 1mol of chlorine is needed for the addition reaction of 1mol of ethylene with chlorine; ch2clch2cl + 4cl2 irradiates ccl3ccl3 + 4hcl, so 1mol of ch2clch2cl needs 4mol of chlorine at most for the substitution reaction of 1mol of ch2clch2cl with chlorine, and the sum of these two parts is 1mol + 4mol = 5mol

Is "+" for filling and "-" for excavation, or "+" for excavation and "-" for filling when calculating earthwork volume
I recently bought a book. When the numbers around the square grid are all "-" numbers, he said excavation, but when there are three "+" numbers around the square grid, he also said excavation ~ I'm a little dizzy ~ so I want to ask

1. In calculation, the values of "+" and "-" are relative to the design elevation, and "+" means that the earth needs to be excavated higher than the design elevation, and the earth needs to be filled on the contrary
2. That is, the value in the grid = actual elevation H1 - design elevation h in the grid

What are the differences between the mass and relative mass of 1mol particles or substances?

The values are the same, but one has a unit and the other does not

What is the basis for measuring the opening line (or toe line) of subgrade excavation (filling)?
How to accurately measure the subgrade slope? I am a novice. The subgrade cross-section map gives the corresponding mileage of the section, the original landform elevation difference directly above the design baseline, the design line offset to the left, the design elevation, the elevation difference between the opening line and the design elevation point, the excavation volume and other data!

1. Use the instrument to loft out the excavation position given in the design. At this time, the elevation must be different from the design elevation
2. The H elevation difference is obtained by the difference between the actual elevation and the design elevation
3. The height difference h is multiplied by the slope to get a width K
4. The excavation position is obtained by measuring K horizontally from the lofting point to the outside of the line
Note: most of the time, four can't be achieved, that is to say, it can't be measured horizontally outwards. At this time, we can talk with the construction personnel on site: how much is the excavation line from this point horizontally outwards, which is relatively simple