1. The problem statement, all variables and given/known data Use Bohr's rule, L=n[itex]\hbar[/itex], to find the quantized speeds, radii, and energies for circular orbits of a particle of mass m bound to the origin by the Hooke's-law force, F(r) = -Kr. 2. Relevant equations mass=m ƩF=ma F(r)=-kr L=n[itex]\hbar[/itex] p=mvr mvr=n[itex]\hbar[/itex] r=n[itex]\hbar[/itex]/mv (a) 3. The attempt at a solution mv²/r=-kr mv²=-kr² (b) subbing (a) into (b) mv²=-kn²[itex]\hbar²[/itex]/m²v² solving for v... (v²)²=-kn²[itex]\hbar²[/itex]/m³ v=(-kn²[itex]\hbar²[/itex]/m³)^¼ and this is where I get stuck because of the negative sign in the 4th root of v. If I make ma=kr it works out, BUT it seems cheap just to change the law from -kr to kr.