8-2-conservation-of-momentum_summary

The section focus on the law of conservation of momentum, a fundamental principle in physics which states that the total momentum in a closed system remains constant before and after a collision, explosion, or other event involving objects in motion. The total momentum is calculated as the sum of the momenta of individual objects within the system. The law is applicable to diverse systems, such as a collision of two cars or a comet striking the Earth, provided that the net external force acting on the system is zero, making it an isolated system. Momentum is only conserved when the entire system affected is taken into account. The conservation of momentum can be understood through the impulse-momentum theorem, which states that the change in momentum (impulse) of an object is equal to the force acting on it multiplied by the time it acts, and that the changes in momentum are equal and opposite in a collision. The law of conservation of momentum can be used to predict the final states of systems after an interaction, such as determining the velocities of cars after a collision. The section also introduces the concept of angular momentum, which describes the tendency of objects in rotational motion to continue in a circular path. Angular momentum is analogous to linear momentum and is conserved when the net external torque acting on the system is zero. Figure skaters, for example, take advantage of the conservation of angular momentum when spinning, as they can increase their rate of spin by reducing their moment of inertia (the rotational inertia or moment of inertia of a point mass at a distance from the center of rotation).