On April 29th, 2009, Chongqing Chaotianmen Yangtze River Bridge, the world's first, was officially opened to traffic (pictured). The main bridge of the bridge is 932m long, and the permanent steel used for the whole bridge has reached the domestic record of 4.6× 107 kg. (The result is an integer).

(1) How much is the permanent steel for bridge? (take g= 10N/kg)

(2) If the pedestrian crossing the bridge walks at a speed of about 1.2m/s, how many s does it take him to cross the main bridge?

(3) A class of students came to visit the bridge and lined up to cross the bridge. The team is 50 meters long. Assuming the team speed is 1.2 m/s, how many s does it take for the team to cross the whole bridge? Test site: calculation of gravity; Velocity formula and its application. Special topic: application problem. Analysis: (1) The gravity of bridge permanent steel can be directly calculated by formula G=mg;

(2) The time spent crossing the main bridge is calculated by the formula t=;

(3) When the team leader enters the bridge, the time starts and the team ends, so the distance traveled by the whole team is the total length of the bridge and the team, and then it can be calculated by the time formula. Solution: (1) g = mg = 4.6×107 kg×10n/kg = 4.6× 65438.

(2) ;

(3) .

Answer: (1) The gravity of permanent steel for bridge is 4.6×108n; ;

(2) If the pedestrian crossing the bridge walks at a speed of about 1.2m/s, it takes him 777 s to cross the main bridge;

(3) A class of students came to visit the bridge and lined up to cross the bridge. The team is 50 meters long. Suppose the speed of the team is 1.2 m/s, and it needs 8 18s. Let the team cross the whole bridge.