Moment required to prevent (free) falling object from rotating 1

[hydtools]

How about accounting for the moment of mA about mO in the initial conditions. There is no information given about the initial conditions just before the drop. The dynamic forces would be additive, or subtractive to the initial conditions.

Once all the bouncing stops there will be the static condition of the spring supporting both masses and mA having a moment about mO.

Ted

 

[chicopee]

Something is a little weird about the design. The mass Ma is on a frictionless pivot, therefore, from the starting point the mass Ma should be resting against the frictionless rod. Am I missing something in the OP?

 

[IRstuff]

Seems like a contrived (homework) problem where the freely rotating arm is intentionally held horizontal prior to dropping. Ostensibly, the entire assemblage will fall at the same rate, BUT, the guide cannot be truly frictionless, so the the arm will likely swing downward, regardless. The pivot could potentially be made nearly frictionless, with high-end bearings or flex-pivots, though.

Seriously, though, are there any real-world problems that have frictionless guides or pivots?

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