University:
Montgomery College
Course:
PHYS 161: General Physics I: Mechanics and Heat
Academic year:

2019
Views:

334

Pages:

2
Author:

Annalise Walters

Collisions: In physics, we separate collisions into several categories: Completely inelastic: the objects stick together after the collision. Kinetic energy is not conserved. Before collision After collision Partially inelastic: the objects separate after they collide, but are deformed in some way. Kinetic energy is not conserved. Before collision After collision Completely elastic: the objects separate and remain unchanged. Kinetic energy is conserved. After collision Before collision Let’s look at some different cases: Completely elastic, object 1 of mass m1 moves with speed v1i , Case 1: object 2 of mass m2 is at rest. After colliding, objects 1 and 2 move with speeds v1f and v2f . m1 v1i Before collision m2 v1f m1 m2 After collision *The net external force on an isolated system is zero. v2f Case 1 (continued): Conservation of momentum: Conservation of energy: 2 Solving: and If , then after the collision, object 1 will be at rest and object 2 will move with the velocity that object 1 had before the collision If direction , then after the collision, both objects will continue moving in the same If , then after the collision, objects 1 and 2 will move in opposite directions (i.e., object 1 will “bounce” off object 2) m1 Case 2: m1 m2 m1 m2 m2 Completely inelastic, object 1 of mass m1 moves with speed v1i , object 2 of mass m2 is at rest. m1 v1i m2 Before collision vf After collision Conservation of momentum: Kinetic energy lost: The greatest energy loss occurs when kinetic energy is lost. . If ≫ , then almost all the