为什么据说两辆移动车辆之间的正面碰撞会导致比将车开进墙壁更多的伤害？驾驶员感受到的力量和产生的能量有何不同？专注于力与能量之间的区别可以帮助理解所涉及的物理学。值得注意的是，这是一个理想化的模型。在情况A中，汽车撞到墙壁上并立即停止，这是完全无弹性的碰撞。由于墙壁不会破裂或移动，因此汽车进入墙壁的全部力量必须到达某个地方。无论是墙壁是如此巨大，以至于它加速/移动不可察觉的数量或根本不移动，在这种情况下，碰撞的力实际上作用于整个行星 – 这显然是如此巨大，以至于效果可以忽略不计。在汽车A与汽车B发生碰撞的情况B中，我们有一些不同的力量考虑因素。假设汽车A和汽车B是彼此完整的镜子（同样，这是一种非常理想化的情况），它们将以完全相同的速度（但是相反的方向）相互碰撞。从保持动力，我们知道他们必须都休息。质量是一样的。因此，轿厢A和轿厢B所经受的力是相同的，并且与在情况A中作用在轿厢上的力相同。因此，每种情况下，每辆轿车在碰撞之前都具有动能K.在碰撞结束时，两辆车都处于静止状态，系统的总动能为0.由于这些是非弹性碰撞，动能不守恒，但总能量总是守恒的，因此动能“丢失” “在碰撞中必须转换成其他形式 – 热量，声音等。在情况A中，只有一辆车在移动，所以在碰撞过程中释放的能量是K.但是，在B情况下，有两辆车在移动，因此碰撞时释放的总能量为2K。因此，案例B中的崩溃显然比案例A崩溃更有活力，这使我们进入下一点。 考虑案例A，其中汽车A与静止的，牢不可破的墙碰撞。情况开始于汽车A以速度v行进并以速度0结束。这种情况的力量由牛顿第二运动定律定义。力等于质量乘以加速度。在这种情况下，加速度是（v-0）/ t，其中t是汽车A停止所需的时间。汽车沿着墙壁的方向施加这种力，但是根据牛顿第三运动定律，墙壁（静止且不易破碎）对汽车施加相同的力。正是这种相等的力量导致汽车在碰撞过程中手风琴式上升。这解释了碰撞的力量，但问题的第二部分 – 碰撞的能量考虑因素。力是矢量，而动能是标量，用公式K = 0.5mv2计算。为什么物理学家会加速对撞机中的粒子来研究高能物理？虽然玻璃瓶在以更高的速度抛出时会碎成较小的碎片，但汽车似乎并没有以这种方式破碎。其中哪些适用于对撞机中的原子？首先，考虑两种情况之间的主要差异非常重要。在粒子的量子水平上，能量和物质基本上可以在状态之间交换。无论多么精力充沛，汽车碰撞的物理特性都不会发出全新的汽车。在这两种情况下，汽车将经历完全相同的力。作用在汽车上的唯一力是由于与另一个物体碰撞而在短时间内从v突然减速到0速度。但是，在查看整个系统时，B情况下的碰撞释放的能量是A碰撞时的两倍。它更大声，更热，更可能更混乱。很有可能，汽车相互融合，碎片沿着随机方向飞散。这就是为什么碰撞两束粒子是有用的，因为在粒子碰撞中你并不真正关心粒子的力（你甚至从未真正测量过），而是关心粒子的能量。粒子加速器可以加快粒子的运动速度，但却具有非常真实的速度限制（由爱因斯坦相对论的光栅速度决定）。为了从碰撞中挤出一些额外的能量，而不是将近光速粒子束与静止物体碰撞，最好将其与另一束相反方向的近光速粒子碰撞。从粒子的角度来看，它们并没有那么“破碎”，但绝对是当两个粒子相互碰撞时，更多的能量被释放出来。在粒子的碰撞中，这种能量可以采取其他粒子的形式，你从碰撞中拉出的能量越多，粒子就越奇特。
Why is it that a head-on collision between two moving vehicles is said to result in more injuries than driving a car into a wall? How do the forces felt by the driver and the energy generated differ? Focusing on the distinction between force and energy can help understand the physics involved. It is important to note that this is an idealized model. In case A, the car slams into the wall and comes to an immediate stop, which is a perfectly inelastic collision. Since the wall doesn’t break or move at all, the full force of the car into the wall has to go somewhere. Either the wall is so massive that it accelerates/moves an imperceptible amount or it doesn’t move at all, in which case the force of the collision actually acts on the entire planet – which is, obviously, so massive that the effects are negligible. In case B, where car A collides with car B, we have some different force considerations. Assuming that car A and car B are complete mirrors of each other (again, this is a highly idealized situation), they would collide with each other going at precisely the same speed (but opposite directions). From conservation of momentum, we know that they must both come to rest. The mass is the same. Therefore, the force experienced by car A and car B are identical and are identical to that acting on the car in case A. In each case, therefore, each car has kinetic energy K directly before the collision. At the end of the collision, both cars are at rest, and the total kinetic energy of the system is 0. Since these are inelastic collisions, the kinetic energy is not conserved, but total energy is always conserved, so the kinetic energy “lost” in the collision has to convert into some other form – heat, sound, etc. In case A, there is only one car moving, so the energy released during the collision is K. In case B, however, there are two cars moving, so the total energy released during the collision is 2K. So the crash in case B is clearly more energetic than the case A crash, which brings us to the next point. Consider case A, in which car A collides with a static, unbreakable wall. The situation begins with car A traveling at a velocity v and it ends with a velocity of 0. The force of this situation is defined by Newton’s second law of motion. Force equals mass times acceleration. In this case, the acceleration is (v – 0)/t, where t is whatever time it takes car A to come to a stop. The car exerts this force in the direction of the wall, but the wall (which is static and unbreakable) exerts an equal force back on the car, per Newton’s third law of motion. It is this equal force which causes cars to accordion up during collisions. This explains the force of the collision, but there is a second part of the question—the energy considerations of the collision. Force is a vector quantity while kinetic energy is a scalar quantity, calculated with the formula K = 0.5mv2. Why do physicists accelerate particles in a collider to study high-energy physics? While glass bottles shatter into smaller shards when thrown at higher speeds, cars don’t seem to shatter in that way. Which of these applies to atoms in a collider? First, it’s important to consider the major differences between the two situations. At the quantum level of particles, energy and matter can basically swap between states. The physics of a car collision will never, no matter how energetic, emit a completely new car. The car would experience exactly the same force in both cases. The only force that acts on the car is the sudden deceleration from v to 0 velocity in a brief period of time, due to the collision with another object. However, when viewing the total system, the collision in case B releases twice as much energy as the case A collision. It’s louder, hotter, and likely messier. In all likelihood, the cars have fused into each other, pieces flying off in random directions. And this is why colliding two beams of particles are useful because in particle collisions you don’t really care about the force of the particles (which you never even really measure), you care instead about the energy of the particles. A particle accelerator speeds particles up but does so with a very real speed limitation (dictated by the speed of light barrier from Einstein’s theory of relativity). To squeeze some extra energy out of the collisions, instead of colliding a beam of near-light speed particles with a stationary object, it’s better to collide it with another beam of near-light speed particles going the opposite direction. From the particle’s standpoint, they don’t so much “shatter more,” but definitely when the two particles collide more energy is released. In collisions of particles, this energy can take the form of other particles, and the more energy you pull out of the collision, the more exotic the particles are.