Why Study Elastic Collisions Despite Their Absence in the Real World

Everything in physics is a simplification of the real world. Leaving out small details and concentrating on the underlying physics allows us to model and understand complex phenomena. While some concepts like perpetual motion remain theoretically beyond our reach, others like elastic collisions provide a valuable framework for understanding the behavior of objects in motion.

Approaching the Ideal

We can APPROACH perpetual motion while never reaching it. The motion of planets or stars continues for billions of years, and we continue to learn more about their dynamics. Similarly, we can APPROACH an elastic collision in the physical world. Even hardened steel loses a very tiny fraction of its energy in a collision, as seen in Newton’s cradle, where the balls swing back and forth indefinitely for a while due to the minimal energy loss.

Near-Elastic Collisions

Near-Elastic Collisions occur when, over a few bounces, only a tiny fraction of energy is lost. For example, when you observe a cheap Newton’s cradle, after some bounces, all the balls eventually swing together. This happens because most of the energy has been dissipated over time. Over the first ten or twenty bounces, however, the collision is very close to being perfectly elastic, as the loss of energy is negligible.

Springs and Energy Transfer

Winding a spring in a clock is an example of a collision where we expect to get back the majority of the energy we put into it. Springs are also important components in collisions involving vertical motion, such as a car hitting a bump. If we permitted the collision to remain elastic, the car would continue to bounce up and down for a long time after each bump. Therefore, we require that the collision be only partly elastic to ensure the car settles smoothly.

Understanding Fundamental Concepts

A full understanding, not just of perfectly elastic and perfectly inelastic collisions, but also of partly elastic collisions and explosions, is crucial to comprehending what actually happens in the real world. This knowledge helps us to better model and predict the behavior of various systems, whether in everyday life or in advanced scientific research. It is unfortunate that many students never reach a beginning level of understanding of these concepts.

Particle Collisions in Physics

In the realm of particle physics, a large fraction of collisions is elastic. The probability of such collisions is expressed by corresponding cross sections and is measured with great precision to tune theoretical models describing these processes. One significant experiment dedicated to this is the TOTEM experiment at CERN, which focuses on measuring elastic and inelastic proton-proton cross sections.

The TOTEM Experiment at CERN

The TOTEM experiment at CERN is a pioneering project aimed at understanding particle collisions at a detailed level. By measuring the elastic and inelastic cross sections, TOTEM helps physicists refine their models and gain insights into the interactions between particles at the fundamental level. This data is crucial for advancing our understanding of particle physics and the behavior of subatomic particles.

Conclusion: While elastic collisions may not perfectly exist in the real world, studying them provides a valuable framework for understanding the intricacies of physical phenomena. The TOTEM experiment at CERN exemplifies how precise measurements and detailed analysis contribute to our ever-growing knowledge in physics.

By striving to learn as much as possible, we move closer to mastering our understanding of these complex systems. This is what distinguished great physicists like Isaac Newton from students, who may feel overwhelmed by the vast amount of knowledge to be acquired. It is not about knowing everything, but about continuously striving to deepen one's understanding.