Chapter 4 Homework

Homework H4.T – Sp26

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Problem statement
Solution video

DISCUSSION THREAD

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Discussion

You are asked to investigate the dynamics of this system during the short time of impact of P with A.

  • It is suggested that you consider a system made up of A+P+bar (make the system “big”).
  • Draw a free body diagram (FBD) of this system.
  • For this system, linear momentum is NOT conserved since there are non-zero reaction forces at O.
  • Furthermore, energy is NOT conserved since there is an impact of P with A during that time.
  • From your FBD of the system, you see that the moment about the fixed point O is zero. What does this say about the angular momentum of the system about O during impact? (Answer: It is conserved!)

HINTS:

STEP 1 – FBD: Draw a SINGLE free body diagram (FBD) of the system of A+P+bar.
STEP 2 – Kinetics:  Consider the discussion above in regard to conservation of angular momentum about point O. Recall how to calculate the angular momentum about a point for a particle.
STEP 3 – Kinematics: At Instant 2, the P sticks to A: vP2 = vA2.
STEP 4 – Solve. 

 

2 thoughts on “Homework H4.T – Sp26”

    1. A and P are particles. They occupy the same point in space. The moment of the weight for either A or P is zero since A and P exist directly below O (no moment about O).

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