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Learn about the Law of Conservation of Momentum, Momentum and Force relation, Collisions, and Energy-Momentum Conservation in collisions. Explore 1-D and 2-D/3-D collision scenarios.
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Law of Conservation of Momentum • This is one of four conservation laws in physics that are very important (charge, energy, and mass also) • We will only study linear momentum (angular momentum is an AP Physics C topic only) • Useful to use for interactions (like collisions)
Momentum and Its Relation to Force • Momentum is the product of an object’s mass and velocity • Units of kg∙m/s • Momentum comes from Newton’s Second Law • The rate of change of momentum (derivative of momentum) is equal to the net force acting on it
Conservation of Momentum • momentum before = momentum after • The total momentum of an isolated system of objects remains constant • System = set of objects chosen that interact with each other • Isolated = the only significant forces are between the objects in the system • i.e., there is no net forces acting on the system • Often occurs in explosions
Collisions and Impulse • Impulse = the product of force and the time over which the force acts • Impulse is the area under an F-t curve
Conservation of Energy and Momentum in Collisions • Elastic Collision = total kinetic energy is conserved • Inelastic Collision = energy is conserved, but is no longer kinetic
1-D Collisions • Elastic Collisions • Inelastic Collisions • True for explosions, or where friction is present • If it is completely inelastic, the objects will stick together
Collision in 2-D or 3-D • Momentum in each direction is conserved • px is conserved, py etc.