1. Science Starter A 2 kg object moving east at 12 m/s collides with a stationary 6 kg object. After the collision, the 2 kg object bounces west at 6 m/s. With what velocity does the 6 kg object move after the collision?

2. Conservation of Momentum During a collision, total momentum does not change:

3. Conservation of Energy in Collisions Momentum is conserved in all collisions. Energy is not necessarily conserved in a collision: - If the initial total kinetic energy is the same as the final total kinetic energy the collision is classified as “ELASTIC” - If kinetic energy is gained or lost as a result of the interaction, the collision is classified as “INELASTIC”

4. Inelastic Collisions With inelastic collisions, some of the initial kinetic energy is lost to: heat, sound, light, compression. It may also be gained during explosions, as there is the addition of chemical or nuclear energy. A perfectly inelastic collision is one where the objects stick together afterwards, so there is only one final velocity.

5. Example 1 A 0.4 kg disk is at rest when a 0.1 kg disk moving at 4 m/s strikes it. After the collision, the 0.1 kg disk continues moving forward at 2 m/s. (a) What is the speed of the 0.4 kg disk after the collision? (b) Is the collision elastic or inelastic? Justify your response.

6. Example 2 A 1 kg object is moving with a velocity of 6 m/s when it collides with a 2 kg object moving in the same direction at 3m/s. The objects experience a perfectly inelastic collision. (a)What is the velocity of the system after the collision? (b)How much energy is dissipated during the collision?