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anhnguyenasd
2 năm trước
Tỉnh công suất của dòng nước chảy qua đập ngăn cao 25m xuống dưới, biết rằng lưu lượng dòng nước là 120m3(khối)/ phút, khối lượng riêng của nước là 1000kg/m3( khối)
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The first traffic control device appeared near the British House of Parliament at the intersection of George and Bridge Streets. The device was made in response to the desire by a Select Committee to use railway signals on highways. The device had lights and it used arms which extended outwards. It was operated manually by a police officer. The signal was 22 feet high and crowned with a gas light. The light was called semaphore and had arms that would extend horizontally that commanded drivers to "Stop" and then the arms would lower to a 45 degrees angle to tell drivers to proceed with "Caution". At night a red light would command "Stop" and a green light wouldmean use "Caution".The man behind this new and different invention was John Peake Knight a railroad engineer. The main reason for the traffic light was that there was an overflow of horse-drawn traffic over Westminster Bridge which forced thousands of pedestrians to walk next to the house of Parliament. But Knight's invention was not to last long. After only a month of use the device exploded and injured the police officer who was operating the light. In the first two decades of the 20th century semaphore traffic signals, like the one in London, were in use all over the United States with each state having its own design of the device. One good example was from Toledo, Ohio in 1908. The words "Stop" and "Go" were in white on a green background and the lights had red and green lenses illuminated by kerosene lamps for night travelers and the arms where eight feet above ground. Controlled by a traffic officer who would blow a whistle before changing the commands on this signal to help alert travelers of the change, the design was also used in Philadelphia and Detroit. The example in Ohio was the first time America tried to use a more visible form of traffic control that evolved the use of semaphore. The device that was used in Ohio was designed based on the use of railroad signals. 1. What was the main purpose of making the first traffic control device? …………………………………………………………………………………………………………… 2. What was the light operated manually by a police officer called? ……………………………………………………………………………………………………………… 3. Why wasn't John Peake Knight's invention to last long? ………………………………………………………………………………………………………… 4. How tall were the arms of the traffic lights used in Ohio in 1908? ……………………………………………………………………………………………………………… 5. The Westminster Bridge is in . ………………………………………………………………………………

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