# What are the fields in this problem?

In problem 3 of chapter 2 of Landau Lifshitz "Mechanics," I don't understand the meaning of the fields as defined in the following statement:

Which components of momentum and angular momentum are conserved in motion in the following fields?

(a) the field of an infinite homogeneous plane,
(b) that of an infinite homogeneous cylinder,
(c) that of an infinite homogeneous prism,
(d) that of two points
etc.

I just don't get what he's trying to say. Does he mean an electric field produced by a uniformly charged infinite plane, or an uniformly charged cylinder, etc.?

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Not sure this question type is appropriate for Stack Exchange, it may be closed. But it doesn't seem like the Author's question has anything to do electric fields. Best of luck. –  Michael Leonard Oct 28 '12 at 22:24
@Michael (and Gilberto) I think it's fine, although we will need some more context from the book to provide an answer. –  David Z Oct 29 '12 at 2:37