linear momentum

momentum

• mass x velocity ; kg ・m/s

• Mass in motion

• changes whenever mass / velocity changes

• velocity points in the same direction as the velocity vector

  • Vector quantity

impulse

• force x time interval ; kg ・m/s

• a small force acting over a long time has the same effect as a large force acting over a short time

• vector that points in the same direction as the force

• when a force acts on an object, it changes the object's momentum

  • newton’s second law

conservation of momentum

• momentum of an object can't change unless an external force acts on the object

• if the total external force acting on a system is zero, then the system's total momentum is conserved (Equilibrium)

• may cause objects to recoil

collisions

• occurs when two objects free from external forces strike one another

• momentum is conserved when objects collide

elastic collision

• kinetic energy is conserved

• the final kinetic energy of the system is equal to its initial kinetic energy

• analyzed using both momentum and kinetic energy conservation

inelastic collision

• collision in which the kinetic energy is not conserved

• the final kinetic energy is less than the initial kinetic energy