It took 50 seconds for a train to pass through a 1140 meter long bridge (from the front of the train to the rear of the train leaving the bridge), and 80 seconds for the train to pass through a 1980 meter long tunnel?

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• 1. There is a road beside the railway parallel to the railway. A 160 meter long train runs eastward at the speed of 54 kilometers per hour. At 7:10 a.m., it meets a worker walking westward and leaves the worker 10 seconds later. At 7:20 a.m., it meets a motorcycle running westward. After 5 seconds, it leaves the motorcycle and asks when it will catch up with the worker?
• 2. How long does it take for a family to go on holiday train with a total length of 250 meters and a speed of 60 kilometers per hour to cross a 500 meter road kkkkkkkk
• 3. What is the maximum length of the road design line
• 4. (1) How many days did it take to build the road? How many days did it take to build the road? (2) How many days has the actual construction period of the road been shortened compared with the original plan? We need to add and subtract fractions This is the complete title: The project team plans to build a 1200 meter long highway. After adopting the new construction scheme, the actual length of the highway built every day is 15 meters longer than the original plan, thus shortening the construction period
• 5. The project team plans to build a 1200 meter long highway. After adopting the new construction scheme, the actual length of the highway built every day is 15 meters longer than the original plan, thus shortening the construction period (1) How many days did it take to build the road? How many days did it take to build the road? (2) How many days has the actual construction period of the road been shortened compared with the original plan?
• 6. A waterworks decided to build a pumping tower by the river to supply water to a and B reservoirs. Please design a line for it to make the length of the water pipe shortest Before 10 o'clock, it's overdue
• 7. In the model test of a certain type of car, the speed of 72 km / h is 80 km on a straight road, and the consumption of gasoline is 5 L. assuming that the gasoline is completely burned, the efficiency of the gasoline engine is 40%. 1. How much heat is released by the complete combustion of gasoline during this journey? 2, What's the main impact? 3. What's the useful power of the car in the process of driving at this speed? The heat of gasoline is 4.6 times 10 to the 7th power, no kilogram of glue, and the density of gasoline is 0.8 times 10 to the 3rd power, no cubic meter
• 8. The car runs at a speed of 90 km / h for 100 km and consumes 8 liters of gasoline. The car runs at a constant speed of 25 km (1) If the efficiency of automobile is 31.25%, what is the useful work of automobile engine? (2) the useful power of automobile engine The calorific value of gasoline is 32 million J / L
• 9. A brand of new car, at the speed of 20 meters per second on the flat road, consumes 10L of gasoline per 100km. The density of gasoline is known It is the third power of ρ = 0.71 × 10, kg / m3 (1) How long does it take for the car to travel at a constant speed of 100km? (2) What is the mass of gasoline consumed by a car for every 100km?
• 10. When a car runs at a constant speed of 72km / h for 10 min, the consumption of gasoline is 1.2kg. When the car runs at a constant speed, the traction force F = 1200n, the consumption of gasoline is 1.2kg A car runs at a speed of 72km / h for 10 min at a constant speed, and consumes 1.2kg of gasoline. The results show that the traction force F is 1.2x103n and the calorific value Q of gasoline is 4.6 x107j / kg. Q: (1) What is the power consumed by the car during this period (that is, the heat released by the complete combustion of gasoline in one second)? (2) What is the power of the car's traction during this period? (3) Compare the results of (1) and (2), what do you find? Briefly analyze the reasons (write two).
• 11. Workers build a road, 10 days later more than 30 meters, the rest of the original speed to continue to build, 9 days can be completed, how long is the road Write the meaning of each equation
• 12. After eight days of building a highway, it is more than 120 meters above the midpoint. The rest will continue to be built at the original speed and can be completed in six days. How long is the highway?
• 13. After six days of building a highway, it is more than 150 meters above the midpoint. The rest will be built at the original speed. How many meters can the highway be completed in five days
• 14. Build a road. After five days, it is more than 160 meters above the midpoint. The rest will continue to be built at the original speed. It can be completed in four days. How long is the road?
• 15. It took six days to build a highway, which was 140 meters above the midpoint. The rest continued to be built at the original speed, and it took another five days to complete. How long is the road?
• 16. The total mileage of expressways in a province is 1400km. If the subgrade width is 50m, how many square meters is the area of expressways in this province? How many square kilometers?
• 17. The design speed of two-way 8-lane expressway is 120km / h, and the general value of subgrade width is 45.00m. Who knows how to get the value?
• 18. Design and build a road, the cross section of the subgrade is trapezoidal ABCD, as shown in the figure (unit: m). Set the height of the subgrade as h, and the slope angles on both sides as α and β, known as H = 2, α = 45 °, Tan β = 12, CD = 10. (1) calculate the width of AB at the base of the road; (2) how much earthwork is required to build such a subgrade 1000 m?
• 19. Road width Why is the width of two lines on the highway three meters
• 20. How wide is the effective width of the road