Momentum+&+Collisions




 * Center of Mass**



I. Collisions - when 2 or more bodies exchange relatively large forces over relatively short periods of time.

II. Impulse and Linear Momentum

A. Single Collision 1. Impulse (J) - change in momentum (delta p) as a result of a collision J= (Unit = (kg-m)/s = N-S 2. Graphically - Forces vs. Time Graph

B. Series of Collisions J = - n (delta)p = - n F(delta)t = - n m(delta)v n = number of projectiles solve for F = -n(delta)p / (delta)t = -(n/(delta)t)(delta)p

III. Types of Collisions (for closed and isolated systems).

A. Inelasatic collisions --> Kinetic Energy is NOT conserved 1. Momentum IS conserved 2. Special Case Completely inelastic collisions --> objects stick together after collision (loose most KE)Ex. Ballistic Pendulum m1v1 + m2v2 = (m1+m2)v1'

B. Elastic collisions - KE IS conserved. NO loss! 1. Momentum is conserved 2. Special Case Collisions between objects of equal mass the velocities switch

C. Stationary Target 1. m1 =m2 exchange velocity 2. massive target (m2>>m1) v1' = -v1 v2' = zero 3. Massive projectile (m1>>m2) v1' = v1 and v2' =2v1

Initial momentum = final momentum ex. m1v1 + m2v2 = m1v1' + m2v2'