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

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

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

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

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

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

On Vector Joining 1 and 2 Closest to larger mass object

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

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