change in momentum
the difference between the final and initial momentum; the mass times the change in velocity
conservation of momentum principle
when the net external force is zero, the total momentum of the system is conserved or constant
elastic collision
a collision that also conserves internal kinetic energy
the average net external force times the time it acts; equal to the change in momentum
inelastic collision
a collision in which internal kinetic energy is not conserved
internal kinetic energy
the sum of the kinetic energies of the objects in a system
isolated system
a system in which the net external force is zero
linear momentum
the product of mass and velocity
perfectly inelastic collision
a collision in which the colliding objects stick together
point masses
structureless particles with no rotation or spin
fundamental constituent of matter and an elementary particle
second law of motion
physical law that states that the net external force equals the change in momentum of a system divided by the time over which it changes