1. CONSERVATION OF MOMENTUM

2. Law of Conservation of Momentum Recall Newton’s 3 rd Law: Every Action has an equal and opposite Reaction: F A = -F B The duration of the collision is the same for both objects: F A ∆t = -F B ∆t F∆t = ∆p, we can substitute the expression for the change in momentum: m A v A2 –m A v A1 = -(m B v B2 -m B v B1 )

3. Law of Conservation of Momentum If you rearrange the previous, you obtain m A v A1 + m B v B1 = m A v A2 + m B v B2 This is the mathematical expression of the LAW OF CONSERVATION OF MOMENTUM.

4. Law of Conservation of Momentum DEFINITION: The Total Momentum of objects before a collision is the same as the Total Momentum of the same objects after the collision. IN OTHER WORDS: The change in momentum in an isolated system is zero. – The objects within the system may interact and exchange momenta, but the total momentum does not change!

5. Collisions in One Dimension NOTE: Momentum is a vector quantity, so both magnitude and direction of the momentum must be conserved.

6. PRACTICE PROBLEMS 1. Go through the model problem p313. 2. Complete #25 and 26 p 315. 3. Complete the practice problems worksheet.