Suggestions:
The problem is naturally broken into two time periods: i) From time of release of plug to a time immediately before impact of plug with block (time 1 to time 2), and ii) from time immediately before impact of plug with block to time immediately after plug is wedged into block (time 2 to time 3).
- From time 1 to time 2: During this time, energy is conserved for the plug. Use this to find the speed of the plug right before impacting block.
- From time 2 to time 3: During this time period, energy is NOT conserved (energy is rarely conserved during impact). However, if you make a system of the sphere, block, plug and arm you will see that there are no non-impulsive forces creating a moment about hinge O. Hence, angular momentum of the system about O is conserved.
3 comments:
You say that angular momentum is conserved, which would mean that there is no moment about "O" correct? But why wouldn't the masses of the two blocks create moments about "O"?
Also, without an initial angle, how do I find the initial position, r_er1
For this problem I used the old relative velocity equations within the new angular impulse equations, where momentum is conserved. For the position, I used the relative positions as vectors for the falling mass, the sphere and the block on the right. I hope this helps.
The masses of the two blocks do create a moment about O. However, they are both within the system, therefore their moments are included in the angular momentum equations and are conserved. There is no moment outside the system to disrupt the conservation.
You won't need an angle. The blocks and bar will be horizontal right before and right after impact.
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