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Oct 30, 2008

Problem 3/233



When trying to solve this problem, I get stuck on how to incorporate the cable/wheel. I can find the momentum of the masses; do I use angular accelerate to solve it? Anybody know what to do?
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3 comments:

CMK said...

Consider the system made up of the 4 spheres and shaft. The cable/pulley creates a moment about the shaft of 0.1*T. Therefore, the angular momentum of the system after t seconds is:

H = integral[ (0.1*T)*dt ]

Find H for each particle using r x (mv) and add together.

Let us know if this helps.

October 30, 2008 at 2:12 PM
kmjones said...

So angular momentum is not conserved in this problem, is that right? The force T creates a moment about O and thus, there is an angular impulse. When calculating for r for each particle, do we assume that the location of the particles in the k direction (being further back on the shaft which is in the negative k direction for me) doesn't have any effect? I ask because we're not given this distance, between the pulley and the particle wheel, and I'm assuming that it will have no effect then. So r would just be the distance radially outward from the shaft?

October 30, 2008 at 2:30 PM
CMK said...

You are correct -- the location of point "O" along the shaft is not important. We interested in the components of moment and momentum about the z-axis (axis of the shaft); moving O along the z-axis does not influence the z-component of either.

For ease, I would choose point O to be the point on the shaft where the spokes are attached. This relieves you of the need to know any distances along the z-axis.

Let me know if this helps.

October 30, 2008 at 4:25 PM

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