After the strong earthquake occurred in Yushu area of Qinghai Province, the state immediately launched the disaster relief plan to actively carry out the transportation of relief materials to the disaster area and the treatment of the wounded. It is known that Xining Airport and Yushu airport are 800 kilometers apart, and plane a and B start from Xining and Yushu along the same route, facing each other. As shown in the figure, line AB and CD respectively indicate that plane a and B leave Yushu airport (Note: for convenience of calculation, the unit of distance s in the plane rectangular coordinate system is set as (100 km)). Observe the image and answer the following questions: (1) how many hours after the departure of plane a, does plane B leave Yushu airport? How many kilometers per hour are the flight speeds of aircraft a and B? (2) (3) when a and B met, how many hours did B fly? How many kilometers from Xining Airport?

After the strong earthquake occurred in Yushu area of Qinghai Province, the state immediately launched the disaster relief plan to actively carry out the transportation of relief materials to the disaster area and the treatment of the wounded. It is known that Xining Airport and Yushu airport are 800 kilometers apart, and plane a and B start from Xining and Yushu along the same route, facing each other. As shown in the figure, line AB and CD respectively indicate that plane a and B leave Yushu airport (Note: for convenience of calculation, the unit of distance s in the plane rectangular coordinate system is set as (100 km)). Observe the image and answer the following questions: (1) how many hours after the departure of plane a, does plane B leave Yushu airport? How many kilometers per hour are the flight speeds of aircraft a and B? (2) (3) when a and B met, how many hours did B fly? How many kilometers from Xining Airport?

(1) It can be seen from the figure that plane B starts from Yushu airport one hour after plane a starts. The flight speed of plane a is V1 = 8005 △ 100 = 1.600 km / h, and the flight speed of plane B is V2 = 8004 △ 100 = 200 km / h. (2) the functional relationship between s and t of plane a is s = − 85t + 8, and the functional relationship between S and t of plane B is s = 2 (t-1) = 2T -

On April 14, 2010, a strong earthquake occurred in Yushu, Qinghai Province. After the earthquake, the aircraft carrying relief materials dropped objects into the disaster area. During the process of the objects falling in the air at a constant speed, the change of their kinetic energy and gravitational potential energy is ()
A. Kinetic energy increases, gravitational potential energy increases B. kinetic energy decreases, gravitational potential energy decreases C. kinetic energy remains unchanged, gravitational potential energy decreases D. kinetic energy remains unchanged, gravitational potential energy increases

The mass, velocity and kinetic energy of the disaster relief articles are unchanged in the process of falling at a constant speed in the air; the height is decreasing and the gravitational potential energy is decreasing