1. Momentum

  2. Types of Forces

    1. Internal: forces between objects in a system
    2. External: forces on objects from outside the system

  3. System

    1. A collection of objects
    2. Open: forces or mass may enter or leave
    3. Closed: no force or mass may enter nor leave
    4. Isolated: no net external forces

  4. Impulse

    1. Product of impact force and impact time
    2. Impulse = (fDt)
    3. Unit: n/s

  5. Momentum

    1. Newton: The quantity of motion
  6. Modern : inertia in motion
    1. Momentum = mass x velocity
    2. P = m • v
    3. Unit: kg•m/s

  7. Impulse and Momentum

    1. F = ma
    2. A = (vf - vi) / Dt
    3. F = m(vf-vi)/Dt
    4. FDt = mvf - mvi
    5. (Mvf -mvi = Dp)

  8. Impulse Momentum Theorem

    1. Impulse of a net force on an object equals the change in momentum
    2. Ft = D mv

  9. Effect of Impulse

    1. Large Dp requires a large impulse
    2. May be large F or long t
    3. Short "t" means high F

  10. Effect of Positive Impulse

    1. Strike object with high force
    2. Maintain contact (follow through)
    3. Large Dp
    4. Ex. Baseball, golf ball

  11. Effect of Negative Impulse

    1. Slow an object
    2. Short time causes high F, greater potential for damage
    3. Control of contact time controls F and thus damage

  12. Question

    1. When a dish falls, will the impulse be less if it lands on a carpet than if it lands on a hard floor? How will the impact be affected?

  13. Question

    1. If the boxer in the previous picture is able to make the impact time 5 times longer by riding the punch, by how much will the force of impace be reduced?

  14. Bouncing

    1. Impulse needed to bring object to stop
    2. Impulse needed to "throw it back"
    3. Impulse of bounce is total of these

  15. Examples

    1. Fallling pot
    2. Pelton wheel;
      1. Cup shaped blades
      2. Bouncing increased force
      3. More effective at grinding ore

  16. Problem Solving

    1. Concepts: ft = mDv, p = mv
    2. Solve for the unknown
    3. Substitute numbers and solve

  17. Types of Collisions: Elastic

    1. Objects collide and the move separately
    2. No external forces
    3. No change in temperature
    4. Energy and p are conserved
  18. Types of Collisions: Inelastic
    1. Objects collide and couple
    2. External forces and temperature change present
    3. P is conserved
    4. Energy is not conserved

  19. Momentum and Collisions

    1. Impulse is a force
    2. By third law, equal impulse in opposite directions
    3. \Momenta are equal and opposite

  20. Law of Conservation

    1. The momentum of a closed, isolated system does not change

  21. Momentum Problems

    1. Concept: pa + pb = p’a + p’b
    2. Mava + mbvb = mav’a + mbv’b
    3. Define the system
    4. Solve for unknown quantity
    5. Substitute numbers and solve

  22. Momentum and Open Systems

    1. Why is it not conserved?
    2. External force may influence system
      1. More impulse
      2. Addition of momentum

  23. Multiple Directions

    1. Pt is the vector sum of individual momenta
    2. Vector sum before = vector sum after collision
    3. Draw diagram
    4. If a = 90º
      1. P’a = p’t cosq
      2. P’b = p’t sin q
    5. If a ¹ 90º resolve vectors into components to solve
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