The two trains leave from station a and station B at the same time. The average passenger train travels 90 kilometers per hour and the average freight train travels 75 kilometers per hour. After () hours, two trains leave Meet 30 kilometers from the midpoint of the two stations

30 * 2 / (90-75) = 4 (hours)
Both vehicles of Party A and Party B drive from two stations at the same time. When they meet, they use the same time. The speed of the bus is 90-75 = 15 (km / h) faster than that of the truck. When they meet, the bus travels 30x2 = 60 km more than the truck, so 60 / 15 = 4 (H)

The speed of a freight car is 5 / 3 of that of a passenger car. Passenger cars travel 80 kilometers more than freight cars per hour, and passenger cars and freight cars travel every

It is set that the speed of passenger cars is V and that of freight cars is 3 / 5V
V (1-3 / 5) = 80 v = 200 km / h bus speed
Truck speed = 120 km / h

A passenger car was traveling at the speed of 72 kilometers per hour. During the driving, the driver of the passenger car found a freight car coming opposite at the speed of 54 kilometers per hour, The bus was traveling at the speed of 72 kilometers per hour. During the driving, the driver of the bus found a truck coming opposite. The speed was 54 kilometers per hour. The truck was 280 meters long. How many seconds did it take for the truck to pass by her?

The bus speed is 72 kilometers per hour, or 20 meters per second
The speed of the truck is 54 kilometers per hour, or 15 meters per second
The relative speed of the two is 20-15 = 5 m / s
Therefore, the passing time = 280 / 5 = 56 seconds

A passenger car was traveling at a speed of 72 kilometers per hour. During the journey, the driver of the passenger car found a freight car opposite, with a speed of 54 kilometers per hour The van passed by him for eight seconds. Ask for the length of the train

Should be
(72 + 54) * 1000 / 3600 * 8 = 280m

Some students took the power train to travel. When the train accelerated evenly on a straight track, one student proposed, "can we use the equipment around us to measure the acceleration of the train?" many students participated in the measurement. The measurement process was as follows: they looked out of the window every 100m While recording the time with a watch, they observed that the time interval from the first landmark to the second landmark is 5S, and the time interval from the first landmark to the third landmark is 9s. Please find out according to their measurement: (1) Acceleration of train; (2) The speed at which they reached the third sign

(1) Study the process of the train from passing the first road sign to passing the second road sign, displacement X1 = 100m, time T1 = 5S, then the speed at the intermediate time is: V1 = x1t1. Similarly, study the process of the train from passing the second road sign to passing the third road sign, displacement X2 = 100m, time T2 = 4S, then the speed at the intermediate time is

Some students travel by high-speed train. When the train accelerates evenly on a straight track, one student proposed: "can we use the equipment around us to measure the acceleration of the train?" many students participated in the measurement. The measurement process is as follows: while looking at the road signs every 100m outside the window, they record the time with their watches, They observed that the time interval from the first landmark to the second landmark is 5S, and the time interval from the first landmark to the third landmark is 9s. Please according to their measurement, then (1) The acceleration of the train is ; (2) Their speed at the third sign is _

The two trains leave from station a and station B at the same time. The average passenger train travels 90 kilometers per hour and the average freight train travels 75 kilometers per hour. After () hours, two trains leave Meet 30 kilometers from the midpoint of the two stations