Linear Momentum Law of Conservation of Momentum This

Linear Momentum

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.