The speed limit of a tunnel is 36km / h. a train is 100m long and runs at the speed of 72km / h. from 50m away from the tunnel, it decelerates evenly and passes through the tunnel at a constant speed not higher than the limit. If the tunnel is 200m long, the following formula can be obtained: 1. The minimum acceleration of the train in uniform deceleration motion 2. The shortest time for all trains to pass through the tunnel Question 2: a car starts to drive on a straight road from a standstill. First, it drives for a distance at an acceleration of A1 = 1.6m/s2, then it moves in a straight line at a constant speed, and then it decelerates at an acceleration of A2 = 6.4m/s2 until it stops. During this period, it advances for a total of 1600 meters and takes 130 seconds (1) The maximum speed of the vehicle in the process (2) If A1 and A2 remain unchanged, the shortest time and the maximum speed required for driving this distance

The speed limit of a tunnel is 36km / h. a train is 100m long and runs at the speed of 72km / h. from 50m away from the tunnel, it decelerates evenly and passes through the tunnel at a constant speed not higher than the limit. If the tunnel is 200m long, the following formula can be obtained: 1. The minimum acceleration of the train in uniform deceleration motion 2. The shortest time for all trains to pass through the tunnel Question 2: a car starts to drive on a straight road from a standstill. First, it drives for a distance at an acceleration of A1 = 1.6m/s2, then it moves in a straight line at a constant speed, and then it decelerates at an acceleration of A2 = 6.4m/s2 until it stops. During this period, it advances for a total of 1600 meters and takes 130 seconds (1) The maximum speed of the vehicle in the process (2) If A1 and A2 remain unchanged, the shortest time and the maximum speed required for driving this distance

(1) The minimum acceleration is just arriving at the tunnel entrance, and the speed is 10m / S (a = 20 ^ 2-10 ^ 2 / 50 = 6m / S ^ 2) (2). The shortest time is that the train always passes through the tunnel at the speed of 10m / S (t = 200 + 100 / 10 = 30s) (2). If the maximum speed is V, then V ^ 2 / 2A1 + vt2 + V ^ 2 / 2A2 = 1600mv / A1 + T2 + V / A2 = 130s (v = T2 =...)

As shown in the figure, when a student was about to cross the road, a car passed at a speed of 72km / h at 100m from the fork
If the width of the road is 12M, can the student completely cross the road before the car reaches the fork with a normal walking speed of 1.5m/s?

Speed: 72km / h = 72000 / 3600 = 20m / S (20m / s)
Distance: the distance before the car reaches the fork is 100m
The time required for the car to reach the fork is: 100 / 20 = 5S
Pedestrian speed: 1.5m/s
The road width is only 12m
The time required to cross the road is: 12 / 1.5 = 8s
It is concluded that the student can't cross the road completely before the car reaches the fork

A car runs at a speed of 72 km / h on a flat road. It starts to climb at this speed. The length of the slope is 100 m, and the speed after climbing is 36 km / h. find the acceleration and time of climbing

According to the velocity displacement formula, V2 − V02 = 2As & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; a = V2 − v022s = 102 − 2022 × 100M / S2 = − 1.5m/s2 & nbsp; the negative sign indicates that the direction is opposite to the initial velocity direction; According to the velocity time formula, t = V − v0a = 10 − 20 − 1.5s = 203s. A: its uphill acceleration is - 1.5m/s2, and the uphill time is 203s

The speed limit of a tunnel is 36km / h, and a train is 100m long. It runs at the speed of 72km / h. when it reaches 75m away from the tunnel, it begins to slow down evenly
Pass through the tunnel at a constant speed not higher than the limit. If the tunnel is 200m long, it is calculated as follows:
1. The minimum acceleration of the train in uniform deceleration motion
2. The shortest time for all trains to pass through the tunnel

The train must be slowed down to 36 km / h within 75 M
10^2=20^2+2a*75
The minimum acceleration of a train in uniform deceleration
a=-2m/s^2
All the trains go through the tunnel
200+100=10t-(1/2)*2t^2
The shortest time t for all trains to pass through the tunnel=