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From the first place to the second place, buses used to take 9 hours. Since the opening of the expressway, the average speed has increased by 40 kilometers per hour, now it only takes 5 hours Hours from a to B. find the distance between a and B
Let the speed of the original car be x km / h
9x=5（x+40）
The solution is x = 50
Then the distance between the two places is 50 * 9 = 450 (km)
On the highway, a car with a length of 4 meters and a speed of 120 km / h is ready to overtake a car with a length of 12 meters and a speed of 100 km / h
On the highway, when a car with a length of 4 meters and a speed of 120 km / h is ready to overtake a truck with a length of 16 meters and a speed of 100 km / h, how many seconds does it take for the car to overtake the truck from the beginning of rear end collision
16m = 0.016km, 4m = 0.004 km, [0.016 + 0.004] / [120-100] = 0.001 hours = 3.6 seconds
The speed of a car is 80 km / h, he said
80km / h
When the vehicle is driving at the speed of 108km / h on the expressway, if the driver's reaction time from finding the abnormal situation on the road ahead to immediately taking emergency braking is 0.4s, and the taxi distance after emergency braking is 75m, at least how much distance should be kept between vehicles for safe driving to avoid rear end collision, Smart people help me. I'll hand it in tomorrow. Please
108km / h = 30m / s, so the reaction time is 0.4 * 30 = 12M, so the distance is 12 + 75 = 87m
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