CK-12-Physics - Intermediate

7.4. Collisions and Conservation Principles http://www.ck12.org

http://demonstrations.wolfram.com/CenterOfMassOfNPoints/

1. Momentum is a vector quantity;~pdefined as the product of mass and velocity:~p=m~v


2. The impulseF∆tis equal to the change in momentum∆p:F∆t=∆p


3. Momentum is a conserved quantity. For any isolated system the change in momentum of the system is zero:
   ∆p= 0


4. The center of mass of an isolated system always moves with constant velocity.


5. The kinetic energy of a system is conserved in elastic collisions.


6. The kinetic energy of a system is not conserved in inelastic collisions; however, momentum is still conserved!


7. In solving for momentum in two dimensions, the momentum must be conserved in each direction.