The discussion revolves around the moment of inertia of a 1220 kg cylindrical object in outer space, specifically questioning whether it can have zero moment of inertia under certain conditions. The context includes references to satellites and their physical properties.
The conversation includes various interpretations of the moment of inertia concept, with some participants providing clarifications regarding the relationship between mass, shape, and moment of inertia. There is no explicit consensus, but guidance has been offered regarding the nature of moment of inertia in relation to physical properties.
Participants note potential confusion regarding the wording of the original problem and the implications of the equations related to torque and angular acceleration. There is an emphasis on understanding the definitions and assumptions involved in the discussion.
Yep, same problem. See my comment in the post above.madchemist said:One of the scheduled activities during a shuttle mission was the launching of the communication satellite. This 1220 kg satellite GEO II is uniform cylinder of a diameter of 1.18 meters and length 1.72 meters. It is identical in mass, density and shape to GEO I which is already orbiting the Earth. Prior to launching, a motor inside the shuttle bay takes one minute to set the satellite spinning from rest to 1.46 rev/s about the cylinder's axis. At this instant the spinning satellite is released from the bay compartment and placed in the same orbit as GEO I. GEO I has zero moment of inertia. (a) Do the two satellites have the same total energy once GEO II is in orbit? If yes, use physics principals to explain why. If no then calculate the difference in energy.
A solid cylinder does. Note that the moment of inertia depends on the axis chosen, but does not depend on whether it's actually rotating or not.madchemist said:In other words, all objects that have matter have non-zero moment of inertia even if they are not rotating?
That makes no sense. You may well be able to solve for the moment of inertia by other means, but not using that approach. It's like saying: The force is zero and the acceleration is zero. So what's the mass?He seems to think that by the equation Torque= Moment of Inertia times Angular Acceleration, he can solve for Moment of Inertia when both Torque and Angular Acceleration are zero.