Passenger car support takes brakes on the pass under a scientific perspective

The process of speeding trucks for passenger cars can be explained in terms of soft collision phenomenon, in which the skill of the driver and truck weight are two decisive factors.

On September 6, Mr. Phan Van Bac drove a truck carrying agricultural products from Da Lat to Ho Chi Minh City. Ho Chi Minh City discovered that the passenger car behind had signs of losing brakes when Bao Loc mountain pass had slowed down so that this car could crash into the rear of his car, and then drove down to 500m safely.

According to physicists, the whole process can be explained in terms of soft collisions , then after collisions, two vehicles are conjoined and have the same speed. In soft collisions, a part of the kinetic energy of a passenger car has successfully transformed the head of the passenger car and the truck tail.

According to the law of conservation of momentum, the speed of the two vehicles after collision is proportional to the total amount of two-stroke momentum before collision and inversely proportional to the total volume of two vehicles. Because the speed of passenger cars is larger than the speed of trucks, immediately after the collision, the truck will suddenly accelerate. It is easy to see if the bigger the truck weight, the smaller the acceleration. In case the truck weight is smaller or equivalent to a passenger car, the truck will be strongly accelerated at the time immediately after the collision resulting in friction with the road surface and may fall off the slope.

Passenger cars crash into the tail of the truck to slow down when losing brakes.(Photo: Hoai Thanh).

The truck has an estimated weight of 9 tons with a cargo volume of about 15 tons, and a 42-seat passenger car with a total weight of about 13 tons. Assuming the passenger car rushes down the slope at a speed of 70km / h (19.4m / s) while the truck has a speed of about 50km / h (13.8m / s), right after the collision of the two vehicles, the same downhill with speed 57km / h (15.8m / s) and the truck is subjected to an instant acceleration of about 2m / s ² .

With such speed and instant acceleration, the truck's braking system is strong enough to be able to handle both vehicles down the safe pass, saving dozens of people on the vehicle.

However, if the car in front is just a small truck or family car weighing about two tons, the consequences will be very catastrophic when the driver controls this vehicle to help the passenger car is plunging down.

At that time, the two cars will go downhill at the speed of 67km / h (18.6m / s) and the small car must be subjected to an instant acceleration of about 5m / s ² , making it easy to be knocked down to the ground. In addition, the brakes of family cars also do not allow to bear a load much larger than the design weight, resulting in rapid braking, and both vehicles may encounter accidents.

According to the drivers and the online community, for the driver to get a passenger car safely downgraded, driver Phan Van Bac handled almost perfectly, combining a choice of relatively equal speeds with passenger cars at collision time to reduce deformation for passenger cars and reduce sudden acceleration to the lowest, while relying on the larger weight of trucks to gradually reduce the speed for two vehicles in the remaining 500m.