What is the working principle of seat belts?

[StEmmanuel]

Seat belts work by using a spiral spring to rotate the spool, keeping the belt tight. The crumple zones are areas at the front and rear of the car that are relatively easier to collapse. When a car hits an obstacle, it does not stop suddenly but absorbs part of the impact force through crumpling (like an empty soda can). The car's cabin is relatively sturdy, so it does not crush the passengers. Instead, it continues to move briefly, causing the front of the car to collide with the obstacle. A seat belt is a highly complex system that works in conjunction with airbags, seats, the steering wheel, and the steering column. During development, it is considered alongside other systems. Take the pre-tensioning force-limiting seat belt as an example: part of the webbing is not pulled out and is instead wound around a cylindrical spool. The device containing this spool is called the retractor. The retractor is installed inside the car body and is generally not visible. Inside the retractor, there is an angle-sensitive mechanism.

[AugustRose]

The working principle of seat belts is actually quite interesting. After years of driving, I feel they are designed based on Newton's laws. Simply put, when you're driving normally, the seat belt allows the webbing to freely extend and retract from the retractor, giving you a comfortable and unrestrained feeling. However, when the vehicle suddenly brakes or is involved in a collision, the sensor inside the retractor detects the change in acceleration and locks the webbing within milliseconds, firmly securing the person in their seat. This prevents the occupant from being thrown forward into the steering wheel or windshield, avoiding serious injuries. Seat belts also feature pretensioners that tighten the webbing just before a collision to reduce slack, along with load limiters that gradually release tension to protect the ribs from excessive impact. This small belt can reduce casualty rates by nearly half, which is why I always remind everyone to buckle up before driving—don't cut corners for convenience. Its brilliance lies in being a silent protector, something used daily that can save lives.

[MacNaomi]

The role of seat belts is something I deeply appreciate in my daily driving. It's not as simple as it looks—during a collision, the seat belt automatically locks. Inside that retractor, there are springs and sensors that trigger the locking mechanism when the vehicle decelerates abruptly, securing the passenger firmly. The principle relies on the physics of inertia—the body wants to keep moving forward, but the belt holds it back. I remember once on the highway when I almost rear-ended another car, and the seat belt instantly tightened, saving me. Even on short trips, don't underestimate it—statistics show drivers who buckle up have significantly higher survival rates in accidents. Newer cars now even come with upgraded pretensioners for faster response. As a driver, I've made it a habit to buckle up immediately, even for slow city driving. It's a free safety net—small actions lead to big safety.

[LaKarter]

The seat belt is crucial for me, especially when traveling with family. Its working principle is that when the car suddenly stops, the seat belt locks through the retractor to keep the person in place and prevent them from being thrown out. The retractor has a sensing device that can respond instantly during a collision. For example, during emergency braking, the belt makes a clicking sound to restrain you, absorbing the impact and reducing injury. Modern cars also have pre-tensioners and load limiters working together, making them more user-friendly. As a parent, I always educate my children to fasten their seat belts because it's simple and effective, reducing the risk of head and chest injuries. Actual tests have shown that it can reduce child casualty rates by over 40%. Developing good habits and not being careless with small things brings peace of mind and convenience.