The length ratio of a and B trains is 4:5. They travel in the same direction. Xiaoming on car a sees that car B has passed from back to front for 20 seconds. How many seconds does Xiaodong on car B see that car B has passed car a?

The length ratio of a and B trains is 4:5. They travel in the same direction. Xiaoming on car a sees that car B has passed from back to front for 20 seconds. How many seconds does Xiaodong on car B see that car B has passed car a?

Hello!
4 / 5 △ 1 / 20 = 16 (seconds)

The passengers in the train can see the trees on the roadside retreating eastward. Taking the ground as the reference, the direction of the train movement is__

The relative motion takes the ground as the reference object, and the tree does not move naturally as well as the ground. The east direction of the tree on the train indicates that the train is moving westward

Passengers in the southbound train see the trees on the roadside retreating. If they also see the car retreating at the same time, what are the movement states of the car based on the ground?

A: the passengers on the train and the train travel south together. Taking the ground as the reference, the car may have three kinds of motion states: ① static, the distance between the car and the train increases, and the car moves backward relative to the train; ② northward, the distance between the car and the train increases, and the car moves backward relative to the train; ③ southward, the distance between the car and the train increases, and the speed of the car must be less than that of the train The speed of the car