Conservation of Conservation of MomentumMomentum

PhysicsPhysicsChapter 6 Section 2 Chapter 6 Section 2

(Pages 215-220)(Pages 215-220)

The Big “MO”The Big “MO”- In all interactions between isolated - In all interactions between isolated

objects, momentum is conservedobjects, momentum is conserved- In every interaction between isolated - In every interaction between isolated

objects, the change in momentum of objects, the change in momentum of the first object is equal to and opposite the first object is equal to and opposite to the change in momentum of the to the change in momentum of the second object.second object.

- Relates to Newton’s Third Law- Relates to Newton’s Third Law

Law of Conservation of Law of Conservation of MomentumMomentum

-The total momentum of all objects -The total momentum of all objects interacting with one another remains interacting with one another remains constant regardless of the nature of constant regardless of the nature of the forces between the objects.the forces between the objects.

Initial momentum = Final Initial momentum = Final momentummomentum mm11vv1i1i + m + m22vv2i2i = m = m11vv1f 1f + m+ m22vv2f2f

Notice how the velocity of the car, and the Notice how the velocity of the car, and the momentum of the car change when the brick is momentum of the car change when the brick is added, but the total momentum is the same.added, but the total momentum is the same.

Chapter 6 Section 2Chapter 6 Section 2HomeworkHomework

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Elastic and Inelastic Elastic and Inelastic Collisions Collisions

PhysicsPhysicsChapter 6 Section 3 Chapter 6 Section 3

(Pages 222-230)(Pages 222-230)

Inelastic CollisionsInelastic Collisions- In a perfectly inelastic collision, two objects - In a perfectly inelastic collision, two objects

stick together and move as one mass after stick together and move as one mass after the collision.the collision.

- Momentum is conserved but kinetic energy - Momentum is conserved but kinetic energy is not conserved in a perfectly inelastic is not conserved in a perfectly inelastic collision.collision.

- In an inelastic collision, kinetic energy is - In an inelastic collision, kinetic energy is converted to internal elastic potential converted to internal elastic potential energy when the objects deform. Some energy when the objects deform. Some kinetic energy is also converted to sound kinetic energy is also converted to sound energy and thermal energy.energy and thermal energy.

Elastic CollisionsElastic Collisions- In an elastic collision, two objects - In an elastic collision, two objects

return to their original shapes and return to their original shapes and move away from the collision move away from the collision separately.separately.

- Both momentum and kinetic energy - Both momentum and kinetic energy are conserved in an elastic collision.are conserved in an elastic collision.

- Few collisions are elastic or perfectly - Few collisions are elastic or perfectly inelasticinelastic

Chapter 6 Section 3Chapter 6 Section 3HomeworkHomework

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