Momentum and collisions in one dimension


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When we speak of "laws" of physics, we are in fact talking about things that seem to always be true, but we cannot in fact claim that these laws dictate how nature works, because we have only limited observations of how the universe works. That said, the Law of the Conservation of Linear Momentum has never failed to describe a closed system of objects. In other words, as long as a system of objects has had no external forces acting on it, we have never seen the total linear momentum of such a system change.

Recall that momentum is defined as Momentum is a vector (with both magnitude and direction), because velocity is a vector. If there are objects in a system, with masses and velocities then the total momentum of the system is

Later, we will be studying the idea of energy. Kinetic energy is the energy associated with velocity. Although momentum is always conserved, kinetic energy is lost in collisions between large objects. A collision where there is no loss of energy is called an elastic collision. A collisions where the colliding objects stick together would be an inelastic collision. You can imagine this by considering two railroad cars colliding. If there are springs mounted on the railroad cars where they collide, the collision will be early elastic. If there were instead a coupling between the cars so that they locked together, it would be inelastic.

We can investigate the conservation of momentum with Scratch-based simulations.

MomentumOfCollisions

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