The train Accelerates along the straight track at a speed of 10.8km/h after passing a road sign

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• 1. The speed of a train is 10.8km/h when it passes a road sign, and it becomes 54km / h after 1min, How long will it take for the train to reach 72 km / h?
• 2. The temperature of the track rises when the train is running on it The teacher said that this is the same as the friction between hands, overcoming the friction to do work I mainly want to understand why the temperature of the rail rises because of work Can it be understood as follows: When the train is running, it overcomes the friction to do work, and the internal energy increases and the temperature rises; Because the friction is mutual, the rail is also subject to friction. If the train is taken as a reference, the rail is moving and works against the friction Is that right?
• 3. It takes 3.5 seconds for a train to pass a road sign and 20 seconds to pass a 300 meter long bridge. It takes a long time for a train to cross an 800 meter long cave______ Seconds
• 4. It takes 6.5 seconds for a train to pass a sign, 23 seconds to pass a 300 meter long bridge, and a few seconds to cross an 800 meter long cave
• 5. It takes 5 seconds for a train to pass a road sign, 20 seconds to pass a 300 meter cave, and how many seconds to pass an 800 meter bridge? Using equation
• 6. It takes 5 seconds for a train to pass a road sign, 20 seconds to pass a 300 meter long bridge, and how many seconds to cross an 800 meter long cave Write the analysis, too
• 7. It takes 3.5 seconds for a train to pass a road sign and 20 seconds to pass a 300 meter long bridge. It takes a long time for a train to cross an 800 meter long cave______ Seconds
• 8. A subway train starts from a static station and moves along a straight line. It first accelerates uniformly with the acceleration A1, and then decelerates uniformly with the acceleration A2 A subway train starts from a static station and moves along a straight line. First, it accelerates uniformly with the acceleration A1, and then decelerates uniformly with the acceleration A2. When it arrives at the station B, it just stops. If the distance between the two stations is x, what is the maximum speed of the train in operation?
• 9. A subway train starts from a station at rest and moves along a straight line. First, it accelerates uniformly with the acceleration A1, then decelerates uniformly with the acceleration A2. When it arrives at station B, it just stops. If the distance between the two stations is x, find the time t
• 10. From the station there is a static train out of the uniform acceleration movement, the first 1 min running 540 m to calculate acceleration~
• 11. The train Accelerates along the straight track at a speed of 10.8 km / h when passing a landmark
• 12. The speed of the train is 10.8km/h when it passes a road sign, and 54km / h after 1min. How long does it take for the train to reach 64.8km/h?
• 13. When a plane takes off and taxis, it starts to make uniform acceleration linear motion from static state, with the acceleration of 4m / S2. When the taxiing speed of the plane reaches 85m / s, it leaves the ground and takes off. If the plane suddenly receives the command from the command tower to stop taking off when it reaches the take-off speed, the pilot immediately stops the plane, and the plane makes uniform deceleration linear motion, with the acceleration of 5m / S2 How long does it take for a plane to reach maximum speed from take-off? (2) How long does the plane take from take-off to stop?
• 14. Recursively seeking the first 30 items of sequence 1 1 3 5 9 17 31 57
• 15. As shown in the figure, in △ ABC, bisectors of ∠ B and ∠ C intersect at point O, and make de ‖ BC through O. if BD + EC = 5, what is de equal to?
• 16. What number should be under the sequence 1,0, - 1,0 Such as the title
• 17. Calculation) 65°53′26〃+37°14′44〃 90°-47°26′15〃 21°32′20〃×4 100°12′15〃÷5 If you can, I'll give you another 20!
• 18. The ratio of chickens to ducks in Uncle Li's family is 5:3. If you raise 300 chickens, how many more chickens are there in Uncle Li's family than ducks? ```The more detailed the better, We need the formula! We need the integrity!
• 19. An English essay about Chinese population To write a short English composition, the simpler the better (but not too simple) 1.What is the population of China? What's the population of China 2.How many people live in the countryside? (how many people live in the countryside) 3.Some parents in less developed areas prefer boys to girls,do not they? In underdeveloped areas, some parents prefer boys to girls, right 4.Can all Chinese families offer their chidren a good education? Can all Chinese families provide good education for their children 5.What is a comfortable life like?How can we make our livesmore comfortable? What is a comfortable life like? How can we make it more comfortable
• 20. The greatest common factor of 15 and 36