# Linear Momentum and Collisions

## Inelastic Collisions in One Dimension


### Learning Objectives

By the end of this section, you will be able to:
1. Define inelastic collision.
2. Explain perfectly inelastic collision.
3. Apply an understanding of collisions to sports.
4. Determine recoil velocity and loss in kinetic energy given mass and initial velocity.
We have seen that in an elastic collision, internal kinetic energy is conserved. An inelastic collision is one in which the internal kinetic energy changes (it is not conserved). This lack of conservation means that the forces between colliding objects may remove or add internal kinetic energy. Work done by internal forces may change the forms of energy within a system. For inelastic collisions, such as when colliding objects stick together, this internal work may transform some internal kinetic energy into heat transfer. Or it may convert stored energy into internal kinetic energy, such as when exploding bolts separate a satellite from its launch vehicle.
 shows an example of an inelastic collision. Two objects that have equal masses head toward one another at equal speeds and then stick together. Their total internal kinetic energy is initially
.  The two objects come to rest after sticking together, conserving momentum. But the internal kinetic energy is zero after the collision. A collision in which the objects stick together is sometimes called a perfectly inelastic collision because it reduces internal kinetic energy more than does any other type of inelastic collision. In fact, such a collision reduces internal kinetic energy to the minimum it can have while still conserving momentum.

### Test Prep for AP Courses


### Section Summary

1. An inelastic collision is one in which the internal kinetic energy changes (it is not conserved).
2. A collision in which the objects stick together is sometimes called perfectly inelastic because it reduces internal kinetic energy more than does any other type of inelastic collision.
3. Sports science and technologies also use physics concepts such as momentum and rotational motion and vibrations.

### Conceptual Questions


### Problems & Exercises
