F=ma 2025 Problem 17

Physics · mechanics

Problem

Question: A particle of mass mm moves in the xy{xy} plane with potential energy U(x,y)=−kx2+y22U(x,y) = -k\frac{x^2 + y^2}{2}. The closest point to the origin (x=0,y=0)(x = 0, y = 0) during its motion was at a distance dd, and the particle's speed at that point was v≠0v \neq 0. Which of the following statements is true regarding the path of the particle after a long time tt (t≫d/vt \gg d/v)? (A) The particle's trajectory will be circular. (B) The particle's trajectory will be asymptotic to a straight line pointing away from the origin. (C) The particle will spiral outwards away from the origin. (D) The particle will travel on a parabolic trajectory. (E) The particle will spiral inwards towards the origin.

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