1. Physics 319 Classical Mechanics
G. A. Krafft
Old Dominion University
Jefferson Lab
Lecture 5
G. A. Krafft
Jefferson Lab

2. Mechanical Momentum System of N particles: (vector) momentum is
As shown in Lecture 2, if there is no net external force acting on the system, momentum is conserved

3. Inelastic Two Body Collision
Momentum before
Momentum after
Collision with stationary object

4. Rockets and Jets Momentum Equation
Thrust vector (force acting on rocket or jet)

5. Rocket Payload Relation
Integrated
Limited velocity (independent how quickly burned!)
In gravity (need results from later in course!)
Therefore important to burn quickly!

6. Center of Mass Definition of Center of Mass for system of N particles
Individual components
Two bodies

7. On Vector Joining 1 and 2
Closest to larger mass object

8. Motion of the Center of Mass
Center of mass of a system of particle moves as if it were a particle with the total mass Mtot concentrated at the center of mass location
For a continuous distribution

9. Example: Center of Mass of a Cone
Center of mass on symmetry axis of cone
Why?
Calculation of Zcm