1. Conservation of Momentum

2. - Law of Conservation of Energy
Remember. . .
Momentum is inertia in motion.
Do you remember the Laws of Conservation that you’ve already learned?
- Law of Conservation of Mass
- Law of Conservation of Energy

3. Law of Conservation of Momentum
A system can contain any number of objects, and the objects can stick together or come apart in the collision.
Under these conditions the Law of Conservation of Momentum states that the momentum of any closed system with no external force does not change.

4. Momentum gets transferred between objects through collisions.

5. m1v1i + m2v2i = m1v1f + m2v2f ELASTIC COLLISIONS ELASTIC:
Both energy & momentum are conserved
Two objects collide and two objects move separately after the collision. (2 to 2)
m1v1i + m2v2i = m1v1f + m2v2f

7. vi (m1+ m2) = m1v1f + m2v2f m1v1i + m2v2i = vf (m1+ m2)
INELASTIC COLLISIONS
INELASTIC:
Momentum conserved, not energy
Lost energy goes to heat
INELASTIC (1 to 2): Two objects have the same initial velocity. After a collision, they split apart and have their own final velocities
vi (m1+ m2) = m1v1f + m2v2f
INELASTIC (2 to 1): Two objects with their own initial velocities collide and stick together, moving with the same final velocity.
m1v1i + m2v2i = vf (m1+ m2)

8. https://youtu.be/ECo5rjYCsGk https://youtu.be/bOM5P0Lr4oM?t=49s

9. Astronaut A (mass 90 kg) pushes Astronaut B (mass 75 kg)
Astronaut A (mass 90 kg) pushes Astronaut B (mass 75 kg).  Astronaut B moves away at 4 m/s

10. Conservation of Momentum Problems

11. Tubby and his twin brother Chubby have a combined mass of 200 kg and are zooming along in a 100 kg amusement park bumper car at 10 m/s. They bump Melinda’s car, which is sitting still. Melinda has a mass of 25 kg. After the elastic collision, the twins continue with a speed of 4.12 m/s. How fast is Melinda’s car bumped across the floor?

12. A 4 kg ball moving at 8 m/s to the right collides with a 1 kg ball at rest. After the collision, the 4 kg ball moves at 4.8 m/s to the right. What is the velocity of the 1 kg ball?

13. A 2,000 kg railroad car moving at 5 m/s to the east collides with a 6,000 kg railroad car moving at 3 m/s to the west. If the cars couple together, what is their velocity after the collision?

14. Anthony and Sissy are participating in the “Roll-A-Rama” roller-skating dance championship. While 75 kg Anthony roller-skates backward at 3 m/s, 60 kg Sissy jumps into his arms with a velocity of 5 m/s in the same direction. How fast does the pair roll backward together?