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Angular momentum and its conservation 
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#1
Jun1211, 09:11 PM

P: 4

1. The problem statement, all variables and given/known data
Check out the attached image. A is a fixed axis. An impulsive force P =FΔT is given to the rod from a distance x. As a reaction to that, an impulsive force P_{A} =F_{A} ΔT is transmitted to A. The rod has a length l and mass M. 2. Relevant equations a. Velocity v of the center of mass G just after the collision. (express in function of P, P_{A} and M ) b. The value of the impulsive force P_{A} (express in function of l, x and P) 3. The attempt at a solution a. I think the center of mass is supposed to translate just after the collision. According to the law of the translating motion: [itex]\sum external forces[/itex] = change in momentum. So, I did P = P_{A} + Mv And I can get v from that. (Am I right here?) What I don't know is: The axis A is fixed ===> The center of mass IS NOT SUPPOSED TO TRANSLATE but ROTATE. If I am thinking of using the angular momentum stuff, I will get a new variable: l (length of the rod). However the question asked if to express v in function of P, P_{A} and M and l is not mentioned. b. NO IDEA. I was thinking of using the angular momentum and apply its conservation but if I call the angular momentum, I will get a new variable M (mass of the rod) which is not asked to use to express P_{A} Looking forward for your help. Tsopa, Japan :D 


#2
Jun1211, 09:23 PM

P: 4

SORRY, I accidentally put the question in the "relevant equations" paragraph (I thought it was "relevant questions" not "equations" lol)
The questions are: a. Express the velocity v of the center of mass G just after the collision. (express in function of P, PA and M ) b. Find the value of the impulsive force PA (express in function of l, x and P) 


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