1. Momentum

2. Momentum = inertia in motion
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3. Moving object has large momentum if
Mass is large (ship moving at slow speed) or
Velocity is large (bullet moving at rapid speed) or
Mass and Velocity are large (massive truck rolling down a steep slope with no brakes)
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4. What is the momentum of the truck if it is NOT moving?
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5. Why are the engines of supertankers turned off when they are 25 km from port?
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6. Changes in momentum may occur:
a change in the mass of an object
a change in velocity,
or both.
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7. bigger Force  bigger Δ in velocity  bigger Δ in momentum
If momentum changes but mass doesn’t
velocity changes….. AND
acceleration occurs.
What produces an acceleration?
FORCE
bigger Force  bigger Δ in velocity  bigger Δ in momentum
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8. Collisions Elastic: Inelastic
colliding objects rebound without deformation or generation of heat
Colliding objects BOUNCE OFF OF EACH OTHER!
Inelastic
Colliding objects become distorted, generate heat, and possibly STICK TOGETHER!
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Momentum

9. Elastic Collisions Moving ball (green) strikes ball at rest (yellow)
Green ball stops, yellow ball moves away
Head-on collision:
Both balls bounce away
Two balls moving in same direction collide
Green moving faster than yellow
Momentum transferred from green ball to yellow
Now yellow ball moving faster
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10. Inelastic Collisions
Sticking together!
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11. Inelastic Collisions
Deformation…………….
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12. You are hovering (REST) next to the space shuttle in earth-orbit
Your buddy of equal mass (moving at 4 m/s) (with respect to the ship) bumps into you.
If she holds onto you, how fast do the two of you move after the collision?
2x mass in motion after collision ½ v
The 2 astronauts move together with a velocity of 2 m/s after the collision.
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13. Conservation of Momentum
momentum before collision = momentum after collision m1v1 = m2v2
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14. Big fish………little fish……
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15. Big fish…..little fish (part 2)
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16. Before collision, momentum of the loaded cart is 150 kg
Before collision, momentum of the loaded cart is 150 kg*cm/s momentum of the dropped brick is 0 kg*cm/s; total system momentum is 150 kg*cm/s.
After the collision, momentum of the loaded cart is 90.0 kg*cm/s momentum of the dropped brick is 60.0 kg*cm/s total system momentum is 150 kg*cm/s.
The momentum lost by the loaded cart (60 kg*cm/s) is gained by the dropped brick.
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17. Before collision, momentum of the cart is 60 kg
Before collision, momentum of the cart is 60 kg*cm/s momentum of the dropped brick is 0 kg*cm/s total system momentum is 60 kg*cm/s.
After the collision, momentum of the cart is 20.0 kg*cm/s momentum of the dropped brick is 40.0 kg*cm/s total system momentum is 60 kg*cm/s.
The momentum lost by the loaded cart (40 kg*cm/s) is gained by the dropped brick.
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Momentum

18. The momentum lost by the car (30 000 kg*m/s) is gained by the truck.
Before the collision, momentum of the car is kg*m/s momentum of the truck is 0 kg*m/s total system momentum is kg*m/s.
After the collision, momentum of the car is kg*m/s momentum of the truck is kg*m/s total system momentum is kg*m/s.
The momentum lost by the car ( kg*m/s) is gained by the truck.
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19. The momentum lost by the truck (30 000 kg*m/s) is gained by the car.
Before the collision, momentum of the truck is kg*m/s momentum of the car is 0 kg*m/s total system momentum is kg*m/s.
After the collision, momentum of the truck is kg*m/s momentum of the car is kg*m/s total system momentum is kg*m/s.
The momentum lost by the truck ( kg*m/s) is gained by the car.
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20. Before the collision, momentum of the car is +20 000 kg
Before the collision, momentum of the car is kg*m/s momentum of the truck is kg*m/s total system momentum is kg*m/s.
After the collision, momentum of the car is kg*m/s momentum of the truck is kg*m/s total system momentum is kg*m/s.
The momentum change of the car ( kg*m/s) is equal in magnitude and opposite in direction to the momentum change of the truck ( kg*m/s) .
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21. Before the collision, momentum of the car is +20 000 kg
Before the collision, momentum of the car is kg*m/s momentum of the truck is kg*m/s total system momentum is kg*m/s.
After the collision, momentum of the car is kg*m/s momentum of the truck is 0 kg*m/s total system momentum is kg*m/s.
The momentum change of the car ( kg*m/s) is equal in magnitude and opposite in direction to the momentum change of the truck ( kg*m/s) .
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23. Sources http://www.physicsplace.com http://www.physicsclassroom.com/
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