I am in AP Physics and my only real hangup is knowing when the said quantities are conserved. Please define what is the SYSTEM in your answer.
I kind of have the basic idea. For example, if there are no external forces, momentum is conserved, and the same is true of torque and angular momentum.
It all just seems so complicated so it would be great if you could clear this up and show me that it's really quite a simple thing.
ONE EXAMPLE of a problem that's tricking me is this:
A 64.0-kg woman stands at the western rim of a horizontal turntable having a moment of inertia of 505 kg · m2 and a radius of 2.00 m. The turntable is initially at rest and is free to rotate about a frictionless, vertical axle through its center. The woman then starts walking around the rim counterclockwise (as viewed from above the system) at a constant speed of 1.50 m/s relative to the Earth. Consider the woman–turntable system as motion begins.
Apparently, angular momentum is conserved but not mechanical energy or regular momentum.
I need some serious help with this.