Conservation of Momentum in Collisions: Exploring Linear and Angular Momentum

[Dale]

My approach to problem solving is to simplify, simplify, simplify.

An approach that I endorse also.

 

[A.T.]

This example is not appropriate, because the body is already moving, and you are not increasing its speed or KE (same applies to orbits, etc.).

This objection is not appropriate, because the spinning gyro is also already moving, and a torque perpendicular to its angular velocity doesn't increase its KE. Just like a force perpendicular to linear velocity doesn't increase KE.

if an object is rotating in one plane it has k KE, if you make it rotate in 2 different planes it has undeniably KE > k, somebody must have given it some KE and therefore must have spent some energy. Is that vague to you? Is this wrong or arguable in any case?

Yes it is wrong. In particular the "undeniably" & "must" part.

 

[Dale]

Since this thread is getting a little tense, and has already gone over 100 posts, the other mentors and I have decided that it is past time to close it.

Bobie, please look at the great advice that you have received from many people and try to actually work out some of the details on the very simplest possible scenarios. Don't assume that you know the answer until you have actually worked out the math.