Chapter 8

• change in momentum the difference between the final and initial momentum; the mass times the change in velocity
• impulse is the product of force and time, measured in newton-seconds (N·s)
• conservation of energy states that the sum of all forms of energy remains constant during an interaction.
• momentum conservation states that when two objects collide, their total momenta are equal to zero.
• conservation of momentum principle when the net external force is zero, the total momentum of the system is conserved or constant
• change in momentum the difference between the final and initial momentum; the mass times the change in velocity
• elastic collision a collision that also conserves internal kinetic energy
• impulse 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
• 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
• point masses structureless particles with no rotation or spin
• quark fundamental constituent of matter and an elementary particle